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	$86.61	3.604%	$89.7314	$89.73	$89.75	$89.70
Purchase #2	$53.30	10.631%	$58.9663	$58.97	$58.95	$59.00
Purchase #3	$130.72	4.160%	$136.158	$136.16	$136.15	$136.20
Purchase #4	$209.64	6.682%	$223.6481	$223.65	$223.65	$223.60
Purchase #5	$117.32	9.435%	$128.3891	$128.39	$128.40	$128.40
Purchase #6	$227.71	3.516%	$235.7163	$235.72	$235.70	$235.70
Purchase #7	$86.89	3.452%	$89.8894	$89.89	$89.90	$89.90
7 purchase totals =	$912.19		$962.4986	$962.51	$962.50	$962.50