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	$211.63	8.485%	$229.5868	$229.59	$229.60	$229.60
Purchase #2	$17.91	10.529%	$19.7957	$19.80	$19.80	$19.80
Purchase #3	$159.98	7.179%	$171.465	$171.47	$171.45	$171.50
Purchase #4	$98.61	8.428%	$106.9209	$106.92	$106.90	$106.90
Purchase #5	$76.30	5.680%	$80.6338	$80.63	$80.65	$80.60
Purchase #6	$118.25	4.747%	$123.8633	$123.86	$123.85	$123.90
Purchase #7	$18.37	11.617%	$20.504	$20.50	$20.50	$20.50
7 purchase totals =	$701.05		$752.7695	$752.77	$752.75	$752.80