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	$160.75	3.299%	$166.0531	$166.05	$166.05	$166.10
Purchase #2	$194.57	6.156%	$206.5477	$206.55	$206.55	$206.50
Purchase #3	$144.97	3.131%	$149.509	$149.51	$149.50	$149.50
Purchase #4	$222.85	9.636%	$244.3238	$244.32	$244.30	$244.30
Purchase #5	$165.98	5.373%	$174.8981	$174.90	$174.90	$174.90
Purchase #6	$27.64	6.672%	$29.4841	$29.48	$29.50	$29.50
Purchase #7	$29.77	9.113%	$32.4829	$32.48	$32.50	$32.50
7 purchase totals =	$946.53		$1,003.2987	$1,003.29	$1,003.30	$1,003.30