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	$35.52	6.355%	$37.7773	$37.78	$37.80	$37.80
Purchase #2	$165.46	4.392%	$172.727	$172.73	$172.75	$172.70
Purchase #3	$73.32	6.741%	$78.2625	$78.26	$78.25	$78.30
Purchase #4	$138.56	9.308%	$151.4572	$151.46	$151.45	$151.50
Purchase #5	$182.90	4.810%	$191.6975	$191.70	$191.70	$191.70
Purchase #6	$14.33	4.474%	$14.9711	$14.97	$14.95	$15.00
Purchase #7	$90.54	6.167%	$96.1236	$96.12	$96.10	$96.10
7 purchase totals =	$700.63		$743.0162	$743.02	$743.00	$743.10