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	$142.72	5.248%	$150.2099	$150.21	$150.20	$150.20
Purchase #2	$223.73	4.593%	$234.0059	$234.01	$234.00	$234.00
Purchase #3	$67.89	4.792%	$71.1433	$71.14	$71.15	$71.10
Purchase #4	$243.78	4.667%	$255.1572	$255.16	$255.15	$255.20
Purchase #5	$67.44	5.345%	$71.0447	$71.04	$71.05	$71.00
Purchase #6	$210.81	8.311%	$228.3304	$228.33	$228.35	$228.30
Purchase #7	$234.40	11.450%	$261.2388	$261.24	$261.25	$261.20
7 purchase totals =	$1,190.77		$1,271.1302	$1,271.13	$1,271.15	$1,271.00