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	$126.47	12.146%	$141.831	$141.83	$141.85	$141.80
Purchase #2	$78.46	9.420%	$85.8509	$85.85	$85.85	$85.90
Purchase #3	$175.88	3.135%	$181.3938	$181.39	$181.40	$181.40
Purchase #4	$37.94	3.846%	$39.3992	$39.40	$39.40	$39.40
Purchase #5	$244.73	10.576%	$270.6126	$270.61	$270.60	$270.60
Purchase #6	$62.91	7.258%	$67.476	$67.48	$67.50	$67.50
Purchase #7	$202.48	5.222%	$213.0535	$213.05	$213.05	$213.10
7 purchase totals =	$928.87		$999.6170	$999.61	$999.65	$999.70