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	$61.93	8.286%	$67.0615	$67.06	$67.05	$67.10
Purchase #2	$80.26	12.426%	$90.2331	$90.23	$90.25	$90.20
Purchase #3	$212.50	4.225%	$221.4781	$221.48	$221.50	$221.50
Purchase #4	$186.30	9.372%	$203.76	$203.76	$203.75	$203.80
Purchase #5	$181.82	3.613%	$188.3892	$188.39	$188.40	$188.40
Purchase #6	$249.57	11.272%	$277.7015	$277.70	$277.70	$277.70
Purchase #7	$173.51	6.791%	$185.2931	$185.29	$185.30	$185.30
7 purchase totals =	$1,145.89		$1,233.9165	$1,233.91	$1,233.95	$1,234.00