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	$81.83	9.408%	$89.5286	$89.53	$89.55	$89.50
Purchase #2	$54.68	12.692%	$61.62	$61.62	$61.60	$61.60
Purchase #3	$185.47	5.498%	$195.6671	$195.67	$195.65	$195.70
Purchase #4	$221.94	7.351%	$238.2548	$238.25	$238.25	$238.30
Purchase #5	$65.89	10.136%	$72.5686	$72.57	$72.55	$72.60
Purchase #6	$70.27	5.183%	$73.9121	$73.91	$73.90	$73.90
Purchase #7	$238.57	5.816%	$252.4452	$252.45	$252.45	$252.40
7 purchase totals =	$918.65		$983.9964	$984.00	$983.95	$984.00