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	$185.69	5.336%	$195.5984	$195.60	$195.60	$195.60
Purchase #2	$247.60	13.688%	$281.4915	$281.49	$281.50	$281.50
Purchase #3	$223.43	12.307%	$250.9275	$250.93	$250.95	$250.90
Purchase #4	$48.59	11.265%	$54.0637	$54.06	$54.05	$54.10
Purchase #5	$64.45	9.109%	$70.3208	$70.32	$70.30	$70.30
Purchase #6	$28.41	7.528%	$30.5487	$30.55	$30.55	$30.50
Purchase #7	$249.61	5.170%	$262.5148	$262.51	$262.50	$262.50
7 purchase totals =	$1,047.78		$1,145.4654	$1,145.46	$1,145.45	$1,145.40