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	$172.94	6.769%	$184.6463	$184.65	$184.65	$184.60
Purchase #2	$66.60	9.477%	$72.9117	$72.91	$72.90	$72.90
Purchase #3	$19.87	6.374%	$21.1365	$21.14	$21.15	$21.10
Purchase #4	$52.33	13.846%	$59.5756	$59.58	$59.60	$59.60
Purchase #5	$197.76	9.411%	$216.3712	$216.37	$216.35	$216.40
Purchase #6	$233.31	5.485%	$246.1071	$246.11	$246.10	$246.10
Purchase #7	$250.57	6.745%	$267.4709	$267.47	$267.45	$267.50
7 purchase totals =	$993.38		$1,068.2193	$1,068.23	$1,068.20	$1,068.20