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	$82.64	9.462%	$90.4594	$90.46	$90.45	$90.50
Purchase #2	$187.98	5.267%	$197.8809	$197.88	$197.90	$197.90
Purchase #3	$140.86	12.613%	$158.6267	$158.63	$158.65	$158.60
Purchase #4	$76.56	7.179%	$82.0562	$82.06	$82.05	$82.10
Purchase #5	$180.39	7.110%	$193.2157	$193.22	$193.20	$193.20
Purchase #6	$119.64	6.785%	$127.7576	$127.76	$127.75	$127.80
Purchase #7	$244.90	11.245%	$272.439	$272.44	$272.45	$272.40
7 purchase totals =	$1,032.97		$1,122.4355	$1,122.45	$1,122.45	$1,122.50