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	$90.70	5.760%	$95.9243	$95.92	$95.90	$95.90
Purchase #2	$10.72	11.241%	$11.925	$11.93	$11.95	$11.90
Purchase #3	$176.81	9.418%	$193.462	$193.46	$193.45	$193.50
Purchase #4	$128.56	12.231%	$144.2842	$144.28	$144.30	$144.30
Purchase #5	$81.59	8.591%	$88.5994	$88.60	$88.60	$88.60
Purchase #6	$122.72	11.363%	$136.6647	$136.66	$136.65	$136.70
Purchase #7	$77.94	6.199%	$82.7715	$82.77	$82.75	$82.80
7 purchase totals =	$689.04		$753.6311	$753.62	$753.60	$753.70