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	$192.33	12.173%	$215.7423	$215.74	$215.75	$215.70
Purchase #2	$161.33	3.134%	$166.3861	$166.39	$166.40	$166.40
Purchase #3	$100.59	11.733%	$112.3922	$112.39	$112.40	$112.40
Purchase #4	$114.27	12.669%	$128.7469	$128.75	$128.75	$128.70
Purchase #5	$115.46	13.414%	$130.9478	$130.95	$130.95	$130.90
Purchase #6	$89.28	6.654%	$95.2207	$95.22	$95.20	$95.20
Purchase #7	$247.62	3.291%	$255.7692	$255.77	$255.75	$255.80
7 purchase totals =	$1,020.88		$1,105.2052	$1,105.21	$1,105.20	$1,105.10