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	$146.99	12.824%	$165.84	$165.84	$165.85	$165.80
Purchase #2	$123.90	7.863%	$133.6423	$133.64	$133.65	$133.60
Purchase #3	$218.25	7.160%	$233.8767	$233.88	$233.90	$233.90
Purchase #4	$43.76	8.512%	$47.4849	$47.48	$47.50	$47.50
Purchase #5	$39.72	8.622%	$43.1447	$43.14	$43.15	$43.10
Purchase #6	$250.41	6.771%	$267.3653	$267.37	$267.35	$267.40
Purchase #7	$227.50	12.208%	$255.2732	$255.27	$255.25	$255.30
7 purchase totals =	$1,050.53		$1,146.6271	$1,146.62	$1,146.65	$1,146.60