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	$190.37	13.127%	$215.3599	$215.36	$215.35	$215.40
Purchase #2	$77.74	9.619%	$85.2178	$85.22	$85.20	$85.20
Purchase #3	$229.59	7.796%	$247.4888	$247.49	$247.50	$247.50
Purchase #4	$138.89	8.140%	$150.1956	$150.20	$150.20	$150.20
Purchase #5	$122.55	13.393%	$138.9631	$138.96	$138.95	$139.00
Purchase #6	$101.96	4.839%	$106.8938	$106.89	$106.90	$106.90
Purchase #7	$247.34	3.674%	$256.4273	$256.43	$256.45	$256.40
7 purchase totals =	$1,108.44		$1,200.5463	$1,200.55	$1,200.55	$1,200.60