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	$59.65	9.270%	$65.1796	$65.18	$65.20	$65.20
Purchase #2	$240.25	12.595%	$270.5095	$270.51	$270.50	$270.50
Purchase #3	$238.65	6.483%	$254.1217	$254.12	$254.10	$254.10
Purchase #4	$113.52	7.588%	$122.1339	$122.13	$122.15	$122.10
Purchase #5	$201.40	11.145%	$223.846	$223.85	$223.85	$223.80
Purchase #6	$166.51	13.647%	$189.2336	$189.23	$189.25	$189.20
Purchase #7	$65.63	8.451%	$71.1764	$71.18	$71.20	$71.20
7 purchase totals =	$1,085.61		$1,196.2007	$1,196.20	$1,196.25	$1,196.10