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	$208.76	3.109%	$215.2503	$215.25	$215.25	$215.30
Purchase #2	$149.41	12.188%	$167.6201	$167.62	$167.60	$167.60
Purchase #3	$32.96	7.729%	$35.5075	$35.51	$35.50	$35.50
Purchase #4	$61.87	13.347%	$70.1278	$70.13	$70.15	$70.10
Purchase #5	$9.52	11.579%	$10.6223	$10.62	$10.60	$10.60
Purchase #6	$135.87	3.123%	$140.1132	$140.11	$140.10	$140.10
Purchase #7	$204.92	11.790%	$229.0801	$229.08	$229.10	$229.10
7 purchase totals =	$803.31		$868.3213	$868.32	$868.30	$868.30