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	$209.38	13.301%	$237.2296	$237.23	$237.25	$237.20
Purchase #2	$126.96	10.513%	$140.3073	$140.31	$140.30	$140.30
Purchase #3	$105.44	12.684%	$118.814	$118.81	$118.80	$118.80
Purchase #4	$127.55	11.417%	$142.1124	$142.11	$142.10	$142.10
Purchase #5	$217.54	5.727%	$229.9985	$230.00	$230.00	$230.00
Purchase #6	$97.98	13.266%	$110.978	$110.98	$111.00	$111.00
Purchase #7	$143.88	5.648%	$152.0063	$152.01	$152.00	$152.00
7 purchase totals =	$1,028.73		$1,131.4461	$1,131.45	$1,131.45	$1,131.40