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	$64.61	12.425%	$72.6378	$72.64	$72.65	$72.60
Purchase #2	$243.92	8.750%	$265.263	$265.26	$265.25	$265.30
Purchase #3	$154.60	9.779%	$169.7183	$169.72	$169.70	$169.70
Purchase #4	$247.27	7.282%	$265.2762	$265.28	$265.30	$265.30
Purchase #5	$206.45	7.838%	$222.6316	$222.63	$222.65	$222.60
Purchase #6	$16.64	13.720%	$18.923	$18.92	$18.90	$18.90
Purchase #7	$78.39	8.496%	$85.05	$85.05	$85.05	$85.10
7 purchase totals =	$1,011.88		$1,099.4999	$1,099.50	$1,099.50	$1,099.50