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	$134.55	9.786%	$147.7171	$147.72	$147.70	$147.70
Purchase #2	$188.59	6.438%	$200.7314	$200.73	$200.75	$200.70
Purchase #3	$143.87	12.774%	$162.248	$162.25	$162.25	$162.20
Purchase #4	$178.29	10.109%	$196.3133	$196.31	$196.30	$196.30
Purchase #5	$37.72	13.171%	$42.6881	$42.69	$42.70	$42.70
Purchase #6	$161.82	13.621%	$183.8615	$183.86	$183.85	$183.90
Purchase #7	$37.58	6.734%	$40.1106	$40.11	$40.10	$40.10
7 purchase totals =	$882.42		$973.6700	$973.67	$973.65	$973.60