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	$188.84	4.283%	$196.928	$196.93	$196.95	$196.90
Purchase #2	$108.91	12.505%	$122.5292	$122.53	$122.55	$122.50
Purchase #3	$245.72	11.239%	$273.3365	$273.34	$273.35	$273.30
Purchase #4	$85.85	10.316%	$94.7063	$94.71	$94.70	$94.70
Purchase #5	$126.88	13.836%	$144.4351	$144.44	$144.45	$144.40
Purchase #6	$52.93	6.459%	$56.3487	$56.35	$56.35	$56.30
Purchase #7	$118.39	10.405%	$130.7085	$130.71	$130.70	$130.70
7 purchase totals =	$927.52		$1,018.9923	$1,019.01	$1,019.05	$1,018.80