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	$125.89	4.268%	$131.263	$131.26	$131.25	$131.30
Purchase #2	$53.93	10.417%	$59.5479	$59.55	$59.55	$59.50
Purchase #3	$216.43	7.788%	$233.2856	$233.29	$233.30	$233.30
Purchase #4	$144.28	11.530%	$160.9155	$160.92	$160.90	$160.90
Purchase #5	$13.82	4.192%	$14.3993	$14.40	$14.40	$14.40
Purchase #6	$130.33	3.396%	$134.756	$134.76	$134.75	$134.80
Purchase #7	$110.86	10.392%	$122.3806	$122.38	$122.40	$122.40
7 purchase totals =	$795.54		$856.5479	$856.56	$856.55	$856.60