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	$170.57	11.832%	$190.7518	$190.75	$190.75	$190.80
Purchase #2	$64.46	6.781%	$68.831	$68.83	$68.85	$68.80
Purchase #3	$33.61	4.275%	$35.0468	$35.05	$35.05	$35.00
Purchase #4	$33.57	12.258%	$37.685	$37.69	$37.70	$37.70
Purchase #5	$210.73	7.642%	$226.834	$226.83	$226.85	$226.80
Purchase #6	$95.57	10.496%	$105.601	$105.60	$105.60	$105.60
Purchase #7	$52.45	13.365%	$59.4599	$59.46	$59.45	$59.50
7 purchase totals =	$660.96		$724.2095	$724.21	$724.25	$724.20