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	$183.36	11.605%	$204.6389	$204.64	$204.65	$204.60
Purchase #2	$213.70	4.700%	$223.7439	$223.74	$223.75	$223.70
Purchase #3	$71.94	12.435%	$80.8857	$80.89	$80.90	$80.90
Purchase #4	$43.33	7.353%	$46.5161	$46.52	$46.50	$46.50
Purchase #5	$148.34	8.174%	$160.4653	$160.47	$160.45	$160.50
Purchase #6	$165.27	13.344%	$187.3236	$187.32	$187.30	$187.30
Purchase #7	$10.70	11.438%	$11.9239	$11.92	$11.90	$11.90
7 purchase totals =	$836.64		$915.4974	$915.50	$915.45	$915.40