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	$222.37	4.838%	$233.1283	$233.13	$233.15	$233.10
Purchase #2	$51.54	6.221%	$54.7463	$54.75	$54.75	$54.70
Purchase #3	$131.73	7.267%	$141.3028	$141.30	$141.30	$141.30
Purchase #4	$158.81	12.422%	$178.5374	$178.54	$178.55	$178.50
Purchase #5	$124.33	11.642%	$138.8045	$138.80	$138.80	$138.80
Purchase #6	$243.77	7.827%	$262.8499	$262.85	$262.85	$262.80
Purchase #7	$60.81	7.518%	$65.3817	$65.38	$65.40	$65.40
7 purchase totals =	$993.36		$1,074.7509	$1,074.75	$1,074.80	$1,074.60