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	$185.95	7.136%	$199.2194	$199.22	$199.20	$199.20
Purchase #2	$53.90	3.529%	$55.8021	$55.80	$55.80	$55.80
Purchase #3	$56.95	10.422%	$62.8853	$62.89	$62.90	$62.90
Purchase #4	$50.78	7.239%	$54.456	$54.46	$54.45	$54.50
Purchase #5	$141.58	4.512%	$147.9681	$147.97	$147.95	$148.00
Purchase #6	$47.44	4.801%	$49.7176	$49.72	$49.70	$49.70
Purchase #7	$89.48	9.245%	$97.7524	$97.75	$97.75	$97.80
7 purchase totals =	$626.08		$667.8009	$667.81	$667.75	$667.90