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	$57.92	3.196%	$59.7711	$59.77	$59.75	$59.80
Purchase #2	$33.57	6.109%	$35.6208	$35.62	$35.60	$35.60
Purchase #3	$168.67	3.261%	$174.1703	$174.17	$174.15	$174.20
Purchase #4	$186.72	13.335%	$211.6191	$211.62	$211.60	$211.60
Purchase #5	$219.37	10.622%	$242.6715	$242.67	$242.65	$242.70
Purchase #6	$83.76	8.573%	$90.9407	$90.94	$90.95	$90.90
Purchase #7	$66.92	4.143%	$69.6925	$69.69	$69.70	$69.70
7 purchase totals =	$816.93		$884.4860	$884.48	$884.40	$884.50