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	$86.87	10.565%	$96.0478	$96.05	$96.05	$96.00
Purchase #2	$39.56	4.861%	$41.483	$41.48	$41.50	$41.50
Purchase #3	$32.86	5.499%	$34.667	$34.67	$34.65	$34.70
Purchase #4	$210.68	13.148%	$238.3802	$238.38	$238.40	$238.40
Purchase #5	$12.53	7.771%	$13.5037	$13.50	$13.50	$13.50
Purchase #6	$93.82	6.134%	$99.5749	$99.57	$99.55	$99.60
Purchase #7	$147.87	9.871%	$162.4662	$162.47	$162.45	$162.50
7 purchase totals =	$624.19		$686.1228	$686.12	$686.10	$686.20