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	$207.96	6.490%	$221.4566	$221.46	$221.45	$221.50
Purchase #2	$67.49	7.437%	$72.5092	$72.51	$72.50	$72.50
Purchase #3	$198.35	10.672%	$219.5179	$219.52	$219.50	$219.50
Purchase #4	$227.73	5.440%	$240.1185	$240.12	$240.10	$240.10
Purchase #5	$83.26	7.558%	$89.5528	$89.55	$89.55	$89.60
Purchase #6	$135.33	12.853%	$152.724	$152.72	$152.70	$152.70
Purchase #7	$77.41	6.769%	$82.6499	$82.65	$82.65	$82.60
7 purchase totals =	$997.53		$1,078.5289	$1,078.53	$1,078.45	$1,078.50