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	$58.92	5.774%	$62.322	$62.32	$62.30	$62.30
Purchase #2	$203.72	6.746%	$217.463	$217.46	$217.45	$217.50
Purchase #3	$239.53	13.583%	$272.0654	$272.07	$272.05	$272.10
Purchase #4	$227.90	5.546%	$240.5393	$240.54	$240.55	$240.50
Purchase #5	$167.47	3.809%	$173.8489	$173.85	$173.85	$173.80
Purchase #6	$62.51	3.685%	$64.8135	$64.81	$64.80	$64.80
Purchase #7	$214.76	4.127%	$223.6231	$223.62	$223.60	$223.60
7 purchase totals =	$1,174.81		$1,254.6752	$1,254.67	$1,254.60	$1,254.60