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	$36.85	13.301%	$41.7514	$41.75	$41.75	$41.80
Purchase #2	$221.39	4.614%	$231.6049	$231.60	$231.60	$231.60
Purchase #3	$184.41	8.191%	$199.515	$199.52	$199.50	$199.50
Purchase #4	$211.79	9.112%	$231.0883	$231.09	$231.10	$231.10
Purchase #5	$76.73	12.716%	$86.487	$86.49	$86.50	$86.50
Purchase #6	$153.54	7.839%	$165.576	$165.58	$165.60	$165.60
Purchase #7	$100.33	8.383%	$108.7407	$108.74	$108.75	$108.70
7 purchase totals =	$985.04		$1,064.7633	$1,064.77	$1,064.80	$1,064.80