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	$195.43	7.822%	$210.7165	$210.72	$210.70	$210.70
Purchase #2	$62.60	13.210%	$70.8695	$70.87	$70.85	$70.90
Purchase #3	$54.45	13.694%	$61.9064	$61.91	$61.90	$61.90
Purchase #4	$59.66	12.678%	$67.2237	$67.22	$67.20	$67.20
Purchase #5	$79.66	7.603%	$85.7165	$85.72	$85.70	$85.70
Purchase #6	$46.49	5.197%	$48.9061	$48.91	$48.90	$48.90
Purchase #7	$170.76	7.436%	$183.4577	$183.46	$183.45	$183.50
7 purchase totals =	$669.05		$728.7964	$728.81	$728.70	$728.80