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	$73.33	4.757%	$76.8183	$76.82	$76.80	$76.80
Purchase #2	$141.38	7.384%	$151.8195	$151.82	$151.80	$151.80
Purchase #3	$220.58	7.651%	$237.4566	$237.46	$237.45	$237.50
Purchase #4	$18.57	8.229%	$20.0981	$20.10	$20.10	$20.10
Purchase #5	$31.46	11.607%	$35.1116	$35.11	$35.10	$35.10
Purchase #6	$90.78	10.435%	$100.2529	$100.25	$100.25	$100.30
Purchase #7	$194.78	9.461%	$213.2081	$213.21	$213.20	$213.20
7 purchase totals =	$770.88		$834.7651	$834.77	$834.70	$834.80