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	$232.82	11.610%	$259.8504	$259.85	$259.85	$259.90
Purchase #2	$102.55	8.377%	$111.1406	$111.14	$111.15	$111.10
Purchase #3	$36.54	6.873%	$39.0514	$39.05	$39.05	$39.10
Purchase #4	$170.97	11.752%	$191.0624	$191.06	$191.05	$191.10
Purchase #5	$52.36	9.228%	$57.1918	$57.19	$57.20	$57.20
Purchase #6	$62.58	3.308%	$64.6501	$64.65	$64.65	$64.70
Purchase #7	$72.53	8.394%	$78.6182	$78.62	$78.60	$78.60
7 purchase totals =	$730.35		$801.5649	$801.56	$801.55	$801.70