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	$197.66	9.517%	$216.4713	$216.47	$216.45	$216.50
Purchase #2	$231.34	3.797%	$240.124	$240.12	$240.10	$240.10
Purchase #3	$39.88	10.185%	$43.9418	$43.94	$43.95	$43.90
Purchase #4	$199.90	12.156%	$224.1998	$224.20	$224.20	$224.20
Purchase #5	$72.77	10.792%	$80.6233	$80.62	$80.60	$80.60
Purchase #6	$100.72	12.312%	$113.1206	$113.12	$113.10	$113.10
Purchase #7	$173.53	7.133%	$185.9079	$185.91	$185.90	$185.90
7 purchase totals =	$1,015.80		$1,104.3887	$1,104.38	$1,104.30	$1,104.30