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	$51.65	9.577%	$56.5965	$56.60	$56.60	$56.60
Purchase #2	$26.37	6.860%	$28.179	$28.18	$28.20	$28.20
Purchase #3	$151.47	10.665%	$167.6243	$167.62	$167.60	$167.60
Purchase #4	$137.78	8.557%	$149.5698	$149.57	$149.55	$149.60
Purchase #5	$145.63	13.864%	$165.8201	$165.82	$165.80	$165.80
Purchase #6	$38.89	7.267%	$41.7161	$41.72	$41.70	$41.70
Purchase #7	$51.76	3.240%	$53.437	$53.44	$53.45	$53.40
7 purchase totals =	$603.55		$662.9428	$662.95	$662.90	$662.90