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	$131.61	3.690%	$136.4664	$136.47	$136.45	$136.50
Purchase #2	$205.62	7.817%	$221.6933	$221.69	$221.70	$221.70
Purchase #3	$110.34	8.791%	$120.04	$120.04	$120.05	$120.00
Purchase #4	$239.39	9.115%	$261.2104	$261.21	$261.20	$261.20
Purchase #5	$141.33	7.572%	$152.0315	$152.03	$152.05	$152.00
Purchase #6	$111.69	13.724%	$127.0183	$127.02	$127.00	$127.00
Purchase #7	$238.47	10.728%	$264.0531	$264.05	$264.05	$264.10
7 purchase totals =	$1,178.45		$1,282.5130	$1,282.51	$1,282.50	$1,282.50