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	$148.79	13.214%	$168.4511	$168.45	$168.45	$168.50
Purchase #2	$127.57	10.860%	$141.4241	$141.42	$141.40	$141.40
Purchase #3	$35.67	4.491%	$37.2719	$37.27	$37.25	$37.30
Purchase #4	$139.48	11.629%	$155.7001	$155.70	$155.70	$155.70
Purchase #5	$126.81	12.520%	$142.6866	$142.69	$142.70	$142.70
Purchase #6	$135.34	13.533%	$153.6556	$153.66	$153.65	$153.70
Purchase #7	$250.73	10.755%	$277.696	$277.70	$277.70	$277.70
7 purchase totals =	$964.39		$1,076.8854	$1,076.89	$1,076.85	$1,077.00