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	$176.79	7.230%	$189.5719	$189.57	$189.55	$189.60
Purchase #2	$78.92	5.539%	$83.2914	$83.29	$83.30	$83.30
Purchase #3	$32.38	7.752%	$34.8901	$34.89	$34.90	$34.90
Purchase #4	$226.72	4.409%	$236.7161	$236.72	$236.70	$236.70
Purchase #5	$241.79	12.634%	$272.3377	$272.34	$272.35	$272.30
Purchase #6	$238.86	12.133%	$267.8409	$267.84	$267.85	$267.80
Purchase #7	$85.61	4.587%	$89.5369	$89.54	$89.55	$89.50
7 purchase totals =	$1,081.07		$1,174.1850	$1,174.19	$1,174.20	$1,174.10