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	$79.90	12.199%	$89.647	$89.65	$89.65	$89.60
Purchase #2	$65.80	11.853%	$73.5993	$73.60	$73.60	$73.60
Purchase #3	$109.83	13.772%	$124.9558	$124.96	$124.95	$125.00
Purchase #4	$46.29	12.631%	$52.1369	$52.14	$52.15	$52.10
Purchase #5	$201.48	10.157%	$221.9443	$221.94	$221.95	$221.90
Purchase #6	$34.67	9.364%	$37.9165	$37.92	$37.90	$37.90
Purchase #7	$233.98	9.497%	$256.2011	$256.20	$256.20	$256.20
7 purchase totals =	$771.95		$856.4009	$856.41	$856.40	$856.30