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	$232.67	11.276%	$258.9059	$258.91	$258.90	$258.90
Purchase #2	$93.70	11.122%	$104.1213	$104.12	$104.10	$104.10
Purchase #3	$142.45	12.804%	$160.6893	$160.69	$160.70	$160.70
Purchase #4	$126.53	6.389%	$134.614	$134.61	$134.60	$134.60
Purchase #5	$164.87	4.776%	$172.7442	$172.74	$172.75	$172.70
Purchase #6	$185.74	6.755%	$198.2867	$198.29	$198.30	$198.30
Purchase #7	$66.36	7.195%	$71.1346	$71.13	$71.15	$71.10
7 purchase totals =	$1,012.32		$1,100.4960	$1,100.49	$1,100.50	$1,100.40