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	$155.38	4.432%	$162.2664	$162.27	$162.25	$162.30
Purchase #2	$45.39	3.271%	$46.8747	$46.87	$46.85	$46.90
Purchase #3	$168.55	8.401%	$182.7099	$182.71	$182.70	$182.70
Purchase #4	$91.62	10.362%	$101.1137	$101.11	$101.10	$101.10
Purchase #5	$101.66	9.677%	$111.4976	$111.50	$111.50	$111.50
Purchase #6	$206.56	12.138%	$231.6323	$231.63	$231.65	$231.60
Purchase #7	$82.51	3.178%	$85.1322	$85.13	$85.15	$85.10
7 purchase totals =	$851.67		$921.2268	$921.22	$921.20	$921.20