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	$114.47	13.711%	$130.165	$130.17	$130.15	$130.20
Purchase #2	$66.89	8.435%	$72.5322	$72.53	$72.55	$72.50
Purchase #3	$232.81	6.294%	$247.4631	$247.46	$247.45	$247.50
Purchase #4	$98.62	12.782%	$111.2256	$111.23	$111.25	$111.20
Purchase #5	$73.45	13.571%	$83.4179	$83.42	$83.40	$83.40
Purchase #6	$123.68	7.703%	$133.2071	$133.21	$133.20	$133.20
Purchase #7	$82.82	8.746%	$90.0634	$90.06	$90.05	$90.10
7 purchase totals =	$792.74		$868.0743	$868.08	$868.05	$868.10