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	$211.33	6.222%	$224.479	$224.48	$224.50	$224.50
Purchase #2	$170.74	11.507%	$190.3871	$190.39	$190.40	$190.40
Purchase #3	$56.65	6.865%	$60.539	$60.54	$60.55	$60.50
Purchase #4	$73.58	8.603%	$79.9101	$79.91	$79.90	$79.90
Purchase #5	$233.86	10.588%	$258.6211	$258.62	$258.60	$258.60
Purchase #6	$31.46	6.412%	$33.4772	$33.48	$33.50	$33.50
Purchase #7	$198.73	4.786%	$208.2412	$208.24	$208.25	$208.20
7 purchase totals =	$976.35		$1,055.6547	$1,055.66	$1,055.70	$1,055.60