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	$226.43	12.272%	$254.2175	$254.22	$254.20	$254.20
Purchase #2	$95.37	13.405%	$108.1543	$108.15	$108.15	$108.20
Purchase #3	$52.63	13.840%	$59.914	$59.91	$59.90	$59.90
Purchase #4	$164.78	13.629%	$187.2379	$187.24	$187.25	$187.20
Purchase #5	$72.87	12.761%	$82.1689	$82.17	$82.15	$82.20
Purchase #6	$239.29	11.736%	$267.3731	$267.37	$267.35	$267.40
Purchase #7	$58.41	11.440%	$65.0921	$65.09	$65.10	$65.10
7 purchase totals =	$909.78		$1,024.1578	$1,024.15	$1,024.10	$1,024.20