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	$112.32	10.680%	$124.3158	$124.32	$124.30	$124.30
Purchase #2	$146.75	10.333%	$161.9137	$161.91	$161.90	$161.90
Purchase #3	$183.94	3.316%	$190.0395	$190.04	$190.05	$190.00
Purchase #4	$40.29	8.441%	$43.6909	$43.69	$43.70	$43.70
Purchase #5	$82.99	6.374%	$88.2798	$88.28	$88.30	$88.30
Purchase #6	$155.71	6.781%	$166.2687	$166.27	$166.25	$166.30
Purchase #7	$161.32	6.826%	$172.3317	$172.33	$172.35	$172.30
7 purchase totals =	$883.32		$946.8401	$946.84	$946.85	$946.80