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	$123.57	5.569%	$130.4516	$130.45	$130.45	$130.50
Purchase #2	$97.76	8.478%	$106.0481	$106.05	$106.05	$106.00
Purchase #3	$63.45	12.732%	$71.5285	$71.53	$71.55	$71.50
Purchase #4	$6.93	7.341%	$7.4387	$7.44	$7.45	$7.40
Purchase #5	$125.77	12.830%	$141.9063	$141.91	$141.90	$141.90
Purchase #6	$180.88	3.669%	$187.5165	$187.52	$187.50	$187.50
Purchase #7	$83.81	6.619%	$89.3574	$89.36	$89.35	$89.40
7 purchase totals =	$682.17		$734.2471	$734.26	$734.25	$734.20