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	$79.39	12.801%	$89.5527	$89.55	$89.55	$89.60
Purchase #2	$176.42	12.415%	$198.3225	$198.32	$198.30	$198.30
Purchase #3	$101.31	10.280%	$111.7247	$111.72	$111.70	$111.70
Purchase #4	$247.31	12.365%	$277.8899	$277.89	$277.90	$277.90
Purchase #5	$94.62	11.858%	$105.84	$105.84	$105.85	$105.80
Purchase #6	$61.30	5.298%	$64.5477	$64.55	$64.55	$64.50
Purchase #7	$20.26	10.438%	$22.3747	$22.37	$22.35	$22.40
7 purchase totals =	$780.61		$870.2522	$870.24	$870.20	$870.20