Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$200.52	11.813%	$224.2074	$224.21	$224.20	$224.20
Purchase #2	$206.78	8.274%	$223.889	$223.89	$223.90	$223.90
Purchase #3	$163.44	10.704%	$180.9346	$180.93	$180.95	$180.90
Purchase #4	$199.56	12.432%	$224.3693	$224.37	$224.35	$224.40
Purchase #5	$190.94	12.106%	$214.0552	$214.06	$214.05	$214.10
Purchase #6	$185.52	5.687%	$196.0705	$196.07	$196.05	$196.10
Purchase #7	$209.51	12.755%	$236.233	$236.23	$236.25	$236.20
7 purchase totals =	$1,356.27		$1,499.7590	$1,499.76	$1,499.75	$1,499.80