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	$189.59	7.320%	$203.468	$203.47	$203.45	$203.50
Purchase #2	$200.28	6.342%	$212.9818	$212.98	$213.00	$213.00
Purchase #3	$243.85	4.837%	$255.645	$255.65	$255.65	$255.60
Purchase #4	$167.66	12.765%	$189.0618	$189.06	$189.05	$189.10
Purchase #5	$101.30	9.708%	$111.1342	$111.13	$111.15	$111.10
Purchase #6	$144.30	5.866%	$152.7646	$152.76	$152.75	$152.80
Purchase #7	$153.43	11.714%	$171.4028	$171.40	$171.40	$171.40
7 purchase totals =	$1,200.41		$1,296.4582	$1,296.45	$1,296.45	$1,296.50