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	$129.96	10.443%	$143.5317	$143.53	$143.55	$143.50
Purchase #2	$67.79	6.460%	$72.1692	$72.17	$72.15	$72.20
Purchase #3	$29.97	3.748%	$31.0933	$31.09	$31.10	$31.10
Purchase #4	$64.51	7.496%	$69.3457	$69.35	$69.35	$69.30
Purchase #5	$14.78	12.396%	$16.6121	$16.61	$16.60	$16.60
Purchase #6	$65.56	10.753%	$72.6097	$72.61	$72.60	$72.60
Purchase #7	$29.27	11.165%	$32.538	$32.54	$32.55	$32.50
7 purchase totals =	$401.84		$437.8997	$437.90	$437.90	$437.80