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	$88.69	7.293%	$95.1582	$95.16	$95.15	$95.20
Purchase #2	$47.49	11.705%	$53.0487	$53.05	$53.05	$53.00
Purchase #3	$140.49	12.693%	$158.3224	$158.32	$158.30	$158.30
Purchase #4	$244.59	12.847%	$276.0125	$276.01	$276.00	$276.00
Purchase #5	$43.30	4.633%	$45.3061	$45.31	$45.30	$45.30
Purchase #6	$118.54	7.840%	$127.8335	$127.83	$127.85	$127.80
Purchase #7	$115.28	3.602%	$119.4324	$119.43	$119.45	$119.40
7 purchase totals =	$798.38		$875.1138	$875.11	$875.10	$875.00