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	$209.57	7.145%	$224.5438	$224.54	$224.55	$224.50
Purchase #2	$249.29	10.419%	$275.2635	$275.26	$275.25	$275.30
Purchase #3	$43.50	6.866%	$46.4867	$46.49	$46.50	$46.50
Purchase #4	$127.31	9.274%	$139.1167	$139.12	$139.10	$139.10
Purchase #5	$168.85	6.148%	$179.2309	$179.23	$179.25	$179.20
Purchase #6	$161.44	9.124%	$176.1698	$176.17	$176.15	$176.20
Purchase #7	$101.62	13.868%	$115.7127	$115.71	$115.70	$115.70
7 purchase totals =	$1,061.58		$1,156.5241	$1,156.52	$1,156.50	$1,156.50