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	$217.86	12.485%	$245.0598	$245.06	$245.05	$245.10
Purchase #2	$162.76	6.432%	$173.2287	$173.23	$173.25	$173.20
Purchase #3	$64.76	12.836%	$73.0726	$73.07	$73.05	$73.10
Purchase #4	$229.77	11.368%	$255.8903	$255.89	$255.90	$255.90
Purchase #5	$131.35	6.519%	$139.9127	$139.91	$139.90	$139.90
Purchase #6	$99.31	4.624%	$103.9021	$103.90	$103.90	$103.90
Purchase #7	$70.93	3.859%	$73.6672	$73.67	$73.65	$73.70
7 purchase totals =	$976.74		$1,064.7334	$1,064.73	$1,064.70	$1,064.80