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	$168.73	13.480%	$191.4748	$191.47	$191.45	$191.50
Purchase #2	$25.97	13.493%	$29.4741	$29.47	$29.45	$29.50
Purchase #3	$139.55	11.587%	$155.7197	$155.72	$155.70	$155.70
Purchase #4	$38.88	11.527%	$43.3617	$43.36	$43.35	$43.40
Purchase #5	$58.33	3.468%	$60.3529	$60.35	$60.35	$60.40
Purchase #6	$73.52	6.211%	$78.0863	$78.09	$78.10	$78.10
Purchase #7	$33.71	3.278%	$34.815	$34.82	$34.80	$34.80
7 purchase totals =	$538.69		$593.2845	$593.28	$593.20	$593.40