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	$72.67	4.344%	$75.8268	$75.83	$75.85	$75.80
Purchase #2	$85.50	4.414%	$89.274	$89.27	$89.25	$89.30
Purchase #3	$211.87	10.557%	$234.2371	$234.24	$234.25	$234.20
Purchase #4	$188.85	13.393%	$214.1427	$214.14	$214.15	$214.10
Purchase #5	$152.37	10.307%	$168.0748	$168.07	$168.05	$168.10
Purchase #6	$165.49	12.342%	$185.9148	$185.91	$185.90	$185.90
Purchase #7	$21.52	6.582%	$22.9364	$22.94	$22.95	$22.90
7 purchase totals =	$898.27		$990.4066	$990.40	$990.40	$990.30