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	$97.80	7.453%	$105.089	$105.09	$105.10	$105.10
Purchase #2	$197.35	5.583%	$208.3681	$208.37	$208.35	$208.40
Purchase #3	$92.61	7.152%	$99.2335	$99.23	$99.25	$99.20
Purchase #4	$127.53	13.528%	$144.7823	$144.78	$144.80	$144.80
Purchase #5	$155.55	5.459%	$164.0415	$164.04	$164.05	$164.00
Purchase #6	$178.89	12.569%	$201.3747	$201.37	$201.35	$201.40
Purchase #7	$88.81	3.772%	$92.1599	$92.16	$92.15	$92.20
7 purchase totals =	$938.54		$1,015.0490	$1,015.04	$1,015.05	$1,015.10