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	$175.48	8.710%	$190.7643	$190.76	$190.75	$190.80
Purchase #2	$60.44	11.102%	$67.15	$67.15	$67.15	$67.20
Purchase #3	$199.50	5.465%	$210.4027	$210.40	$210.40	$210.40
Purchase #4	$37.82	13.562%	$42.9491	$42.95	$42.95	$42.90
Purchase #5	$115.98	6.563%	$123.5918	$123.59	$123.60	$123.60
Purchase #6	$46.98	6.703%	$50.1291	$50.13	$50.15	$50.10
Purchase #7	$68.59	8.681%	$74.5443	$74.54	$74.55	$74.50
7 purchase totals =	$704.79		$759.5313	$759.52	$759.55	$759.50