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	$61.54	12.355%	$69.1433	$69.14	$69.15	$69.10
Purchase #2	$148.59	13.333%	$168.4015	$168.40	$168.40	$168.40
Purchase #3	$244.65	12.525%	$275.2924	$275.29	$275.30	$275.30
Purchase #4	$113.67	7.675%	$122.3942	$122.39	$122.40	$122.40
Purchase #5	$181.75	8.235%	$196.7171	$196.72	$196.70	$196.70
Purchase #6	$113.61	6.266%	$120.7288	$120.73	$120.75	$120.70
Purchase #7	$136.32	10.604%	$150.7754	$150.78	$150.80	$150.80
7 purchase totals =	$1,000.13		$1,103.4527	$1,103.45	$1,103.50	$1,103.40