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	$244.54	6.465%	$260.3495	$260.35	$260.35	$260.30
Purchase #2	$207.82	7.343%	$223.0802	$223.08	$223.10	$223.10
Purchase #3	$210.91	6.816%	$225.2856	$225.29	$225.30	$225.30
Purchase #4	$30.83	13.668%	$35.0438	$35.04	$35.05	$35.00
Purchase #5	$71.69	9.461%	$78.4726	$78.47	$78.45	$78.50
Purchase #6	$55.38	7.116%	$59.3208	$59.32	$59.30	$59.30
Purchase #7	$13.72	3.757%	$14.2355	$14.24	$14.25	$14.20
7 purchase totals =	$834.89		$895.7880	$895.79	$895.80	$895.70