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	$141.50	5.791%	$149.6943	$149.69	$149.70	$149.70
Purchase #2	$143.43	7.286%	$153.8803	$153.88	$153.90	$153.90
Purchase #3	$125.45	4.528%	$131.1304	$131.13	$131.15	$131.10
Purchase #4	$7.26	12.443%	$8.1634	$8.16	$8.15	$8.20
Purchase #5	$149.47	10.317%	$164.8908	$164.89	$164.90	$164.90
Purchase #6	$37.65	12.316%	$42.287	$42.29	$42.30	$42.30
Purchase #7	$143.93	8.866%	$156.6908	$156.69	$156.70	$156.70
7 purchase totals =	$748.69		$806.7370	$806.73	$806.80	$806.80