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	$170.64	9.706%	$187.2023	$187.20	$187.20	$187.20
Purchase #2	$95.28	6.629%	$101.5961	$101.60	$101.60	$101.60
Purchase #3	$232.28	5.278%	$244.5397	$244.54	$244.55	$244.50
Purchase #4	$182.42	9.136%	$199.0859	$199.09	$199.10	$199.10
Purchase #5	$37.81	13.381%	$42.8694	$42.87	$42.85	$42.90
Purchase #6	$100.54	11.146%	$111.7462	$111.75	$111.75	$111.70
Purchase #7	$26.46	5.301%	$27.8626	$27.86	$27.85	$27.90
7 purchase totals =	$845.43		$914.9022	$914.91	$914.90	$914.90