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	$215.96	5.320%	$227.4491	$227.45	$227.45	$227.40
Purchase #2	$159.48	4.598%	$166.8129	$166.81	$166.80	$166.80
Purchase #3	$244.59	11.155%	$271.874	$271.87	$271.85	$271.90
Purchase #4	$194.40	3.311%	$200.8366	$200.84	$200.85	$200.80
Purchase #5	$234.59	8.119%	$253.6364	$253.64	$253.65	$253.60
Purchase #6	$54.80	4.604%	$57.323	$57.32	$57.30	$57.30
Purchase #7	$136.33	11.293%	$151.7257	$151.73	$151.75	$151.70
7 purchase totals =	$1,240.15		$1,329.6577	$1,329.66	$1,329.65	$1,329.50