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	$68.80	5.846%	$72.822	$72.82	$72.80	$72.80
Purchase #2	$128.64	13.379%	$145.8507	$145.85	$145.85	$145.90
Purchase #3	$148.61	4.800%	$155.7433	$155.74	$155.75	$155.70
Purchase #4	$241.35	5.360%	$254.2864	$254.29	$254.30	$254.30
Purchase #5	$209.38	11.514%	$233.488	$233.49	$233.50	$233.50
Purchase #6	$99.42	11.455%	$110.8086	$110.81	$110.80	$110.80
Purchase #7	$61.51	4.345%	$64.1826	$64.18	$64.20	$64.20
7 purchase totals =	$957.71		$1,037.1816	$1,037.18	$1,037.20	$1,037.20