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	$182.73	3.611%	$189.3284	$189.33	$189.35	$189.30
Purchase #2	$167.49	4.620%	$175.228	$175.23	$175.25	$175.20
Purchase #3	$227.75	9.734%	$249.9192	$249.92	$249.90	$249.90
Purchase #4	$144.38	3.109%	$148.8688	$148.87	$148.85	$148.90
Purchase #5	$45.89	3.869%	$47.6655	$47.67	$47.65	$47.70
Purchase #6	$138.85	9.138%	$151.5381	$151.54	$151.55	$151.50
Purchase #7	$131.66	7.206%	$141.1474	$141.15	$141.15	$141.10
7 purchase totals =	$1,038.75		$1,103.6954	$1,103.71	$1,103.70	$1,103.60