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	$156.72	6.626%	$167.1043	$167.10	$167.10	$167.10
Purchase #2	$91.68	6.516%	$97.6539	$97.65	$97.65	$97.70
Purchase #3	$131.32	10.362%	$144.9274	$144.93	$144.95	$144.90
Purchase #4	$71.82	8.337%	$77.8076	$77.81	$77.80	$77.80
Purchase #5	$159.64	7.762%	$172.0313	$172.03	$172.05	$172.00
Purchase #6	$190.25	7.393%	$204.3152	$204.32	$204.30	$204.30
Purchase #7	$55.88	6.748%	$59.6508	$59.65	$59.65	$59.70
7 purchase totals =	$857.31		$923.4905	$923.49	$923.50	$923.50