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	$133.67	5.302%	$140.7572	$140.76	$140.75	$140.80
Purchase #2	$248.43	12.281%	$278.9397	$278.94	$278.95	$278.90
Purchase #3	$213.45	7.682%	$229.8472	$229.85	$229.85	$229.80
Purchase #4	$244.47	4.828%	$256.273	$256.27	$256.25	$256.30
Purchase #5	$131.63	9.837%	$144.5784	$144.58	$144.60	$144.60
Purchase #6	$49.60	9.630%	$54.3765	$54.38	$54.40	$54.40
Purchase #7	$92.29	8.294%	$99.9445	$99.94	$99.95	$99.90
7 purchase totals =	$1,113.54		$1,204.7165	$1,204.72	$1,204.75	$1,204.70