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	$185.83	4.766%	$194.6867	$194.69	$194.70	$194.70
Purchase #2	$32.76	9.657%	$35.9236	$35.92	$35.90	$35.90
Purchase #3	$93.89	11.819%	$104.9869	$104.99	$105.00	$105.00
Purchase #4	$241.95	11.516%	$269.813	$269.81	$269.80	$269.80
Purchase #5	$39.36	7.750%	$42.4104	$42.41	$42.40	$42.40
Purchase #6	$144.55	12.606%	$162.772	$162.77	$162.75	$162.80
Purchase #7	$153.81	9.561%	$168.5158	$168.52	$168.50	$168.50
7 purchase totals =	$892.15		$979.1084	$979.11	$979.05	$979.10