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	$237.65	5.779%	$251.3838	$251.38	$251.40	$251.40
Purchase #2	$93.80	7.429%	$100.7684	$100.77	$100.75	$100.80
Purchase #3	$60.77	10.669%	$67.2536	$67.25	$67.25	$67.30
Purchase #4	$140.40	3.123%	$144.7847	$144.78	$144.80	$144.80
Purchase #5	$140.91	6.337%	$149.8395	$149.84	$149.85	$149.80
Purchase #6	$221.75	8.590%	$240.7983	$240.80	$240.80	$240.80
Purchase #7	$98.73	7.230%	$105.8682	$105.87	$105.85	$105.90
7 purchase totals =	$994.01		$1,060.6965	$1,060.69	$1,060.70	$1,060.80