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	$50.30	10.404%	$55.5332	$55.53	$55.55	$55.50
Purchase #2	$75.44	3.290%	$77.922	$77.92	$77.90	$77.90
Purchase #3	$210.55	10.672%	$233.0199	$233.02	$233.00	$233.00
Purchase #4	$160.89	5.401%	$169.5797	$169.58	$169.60	$169.60
Purchase #5	$54.78	13.755%	$62.315	$62.32	$62.30	$62.30
Purchase #6	$136.99	3.772%	$142.1573	$142.16	$142.15	$142.20
Purchase #7	$118.71	12.514%	$133.5654	$133.57	$133.55	$133.60
7 purchase totals =	$807.66		$874.0925	$874.10	$874.05	$874.10