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	$237.86	5.320%	$250.5142	$250.51	$250.50	$250.50
Purchase #2	$76.96	4.612%	$80.5094	$80.51	$80.50	$80.50
Purchase #3	$58.77	5.431%	$61.9618	$61.96	$61.95	$62.00
Purchase #4	$151.56	8.466%	$164.3911	$164.39	$164.40	$164.40
Purchase #5	$51.38	5.395%	$54.152	$54.15	$54.15	$54.20
Purchase #6	$118.55	11.106%	$131.7162	$131.72	$131.70	$131.70
Purchase #7	$182.25	3.206%	$188.0929	$188.09	$188.10	$188.10
7 purchase totals =	$877.33		$931.3376	$931.33	$931.30	$931.40