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	$149.56	11.499%	$166.7579	$166.76	$166.75	$166.80
Purchase #2	$141.47	8.415%	$153.3747	$153.37	$153.35	$153.40
Purchase #3	$184.95	10.577%	$204.5122	$204.51	$204.50	$204.50
Purchase #4	$67.69	13.822%	$77.0461	$77.05	$77.05	$77.00
Purchase #5	$83.51	7.638%	$89.8885	$89.89	$89.90	$89.90
Purchase #6	$233.98	5.234%	$246.2265	$246.23	$246.25	$246.20
Purchase #7	$96.38	4.531%	$100.747	$100.75	$100.75	$100.70
7 purchase totals =	$957.54		$1,038.5529	$1,038.56	$1,038.55	$1,038.50