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	$75.84	9.483%	$83.0319	$83.03	$83.05	$83.00
Purchase #2	$240.93	13.313%	$273.005	$273.01	$273.00	$273.00
Purchase #3	$63.89	12.478%	$71.8622	$71.86	$71.85	$71.90
Purchase #4	$169.39	12.246%	$190.1335	$190.13	$190.15	$190.10
Purchase #5	$220.85	10.547%	$244.143	$244.14	$244.15	$244.10
Purchase #6	$61.54	9.352%	$67.2952	$67.30	$67.30	$67.30
Purchase #7	$120.56	10.503%	$133.2224	$133.22	$133.20	$133.20
7 purchase totals =	$953.00		$1,062.6932	$1,062.69	$1,062.70	$1,062.60