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	$96.97	4.569%	$101.4006	$101.40	$101.40	$101.40
Purchase #2	$52.33	4.171%	$54.5127	$54.51	$54.50	$54.50
Purchase #3	$215.45	3.382%	$222.7365	$222.74	$222.75	$222.70
Purchase #4	$220.38	6.468%	$234.6342	$234.63	$234.65	$234.60
Purchase #5	$143.55	11.349%	$159.8415	$159.84	$159.85	$159.80
Purchase #6	$50.52	8.761%	$54.9461	$54.95	$54.95	$54.90
Purchase #7	$85.48	4.754%	$89.5437	$89.54	$89.55	$89.50
7 purchase totals =	$864.68		$917.6153	$917.61	$917.65	$917.40