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	$159.27	3.830%	$165.37	$165.37	$165.35	$165.40
Purchase #2	$62.48	8.553%	$67.8239	$67.82	$67.80	$67.80
Purchase #3	$111.69	3.376%	$115.4607	$115.46	$115.45	$115.50
Purchase #4	$83.90	8.118%	$90.711	$90.71	$90.70	$90.70
Purchase #5	$64.85	7.867%	$69.9517	$69.95	$69.95	$70.00
Purchase #6	$186.87	7.191%	$200.3078	$200.31	$200.30	$200.30
Purchase #7	$247.54	6.822%	$264.4272	$264.43	$264.45	$264.40
7 purchase totals =	$916.60		$974.0523	$974.05	$974.00	$974.10