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	$130.49	5.278%	$137.3773	$137.38	$137.40	$137.40
Purchase #2	$67.87	4.847%	$71.1597	$71.16	$71.15	$71.20
Purchase #3	$126.82	3.820%	$131.6645	$131.66	$131.65	$131.70
Purchase #4	$183.54	11.289%	$204.2598	$204.26	$204.25	$204.30
Purchase #5	$98.51	7.647%	$106.0431	$106.04	$106.05	$106.00
Purchase #6	$225.46	13.160%	$255.1305	$255.13	$255.15	$255.10
Purchase #7	$231.90	13.524%	$263.2622	$263.26	$263.25	$263.30
7 purchase totals =	$1,064.59		$1,168.8971	$1,168.89	$1,168.90	$1,169.00