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	$83.77	5.430%	$88.3187	$88.32	$88.30	$88.30
Purchase #2	$73.34	13.228%	$83.0414	$83.04	$83.05	$83.00
Purchase #3	$126.40	8.163%	$136.718	$136.72	$136.70	$136.70
Purchase #4	$182.86	9.539%	$200.303	$200.30	$200.30	$200.30
Purchase #5	$37.76	4.129%	$39.3191	$39.32	$39.30	$39.30
Purchase #6	$53.54	4.786%	$56.1024	$56.10	$56.10	$56.10
Purchase #7	$139.78	7.419%	$150.1503	$150.15	$150.15	$150.20
7 purchase totals =	$697.45		$753.9529	$753.95	$753.90	$753.90