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	$42.28	5.438%	$44.5792	$44.58	$44.60	$44.60
Purchase #2	$98.39	11.180%	$109.39	$109.39	$109.40	$109.40
Purchase #3	$214.27	4.315%	$223.5158	$223.52	$223.50	$223.50
Purchase #4	$218.48	8.391%	$236.8127	$236.81	$236.80	$236.80
Purchase #5	$113.32	9.299%	$123.8576	$123.86	$123.85	$123.90
Purchase #6	$197.76	10.319%	$218.1669	$218.17	$218.15	$218.20
Purchase #7	$180.86	8.859%	$196.8824	$196.88	$196.90	$196.90
7 purchase totals =	$1,065.36		$1,153.2046	$1,153.21	$1,153.20	$1,153.30