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	$245.32	7.573%	$263.8981	$263.90	$263.90	$263.90
Purchase #2	$83.28	9.107%	$90.8643	$90.86	$90.85	$90.90
Purchase #3	$203.47	5.201%	$214.0525	$214.05	$214.05	$214.10
Purchase #4	$5.77	13.272%	$6.5358	$6.54	$6.55	$6.50
Purchase #5	$203.70	9.383%	$222.8132	$222.81	$222.80	$222.80
Purchase #6	$225.82	4.868%	$236.8129	$236.81	$236.80	$236.80
Purchase #7	$33.40	12.818%	$37.6812	$37.68	$37.70	$37.70
7 purchase totals =	$1,000.76		$1,072.6580	$1,072.65	$1,072.65	$1,072.70