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	$71.30	9.572%	$78.1248	$78.12	$78.10	$78.10
Purchase #2	$29.47	10.761%	$32.6413	$32.64	$32.65	$32.60
Purchase #3	$189.79	8.833%	$206.5542	$206.55	$206.55	$206.60
Purchase #4	$223.86	8.690%	$243.3134	$243.31	$243.30	$243.30
Purchase #5	$150.83	6.166%	$160.1302	$160.13	$160.15	$160.10
Purchase #6	$46.44	9.605%	$50.9006	$50.90	$50.90	$50.90
Purchase #7	$233.61	12.743%	$263.3789	$263.38	$263.40	$263.40
7 purchase totals =	$945.30		$1,035.0434	$1,035.03	$1,035.05	$1,035.00