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	$92.32	13.318%	$104.6152	$104.62	$104.60	$104.60
Purchase #2	$99.57	4.301%	$103.8525	$103.85	$103.85	$103.90
Purchase #3	$84.48	6.383%	$89.8724	$89.87	$89.85	$89.90
Purchase #4	$127.26	5.527%	$134.2937	$134.29	$134.30	$134.30
Purchase #5	$145.56	11.358%	$162.0927	$162.09	$162.10	$162.10
Purchase #6	$14.61	9.159%	$15.9481	$15.95	$15.95	$15.90
Purchase #7	$184.35	7.427%	$198.0417	$198.04	$198.05	$198.00
7 purchase totals =	$748.15		$808.7163	$808.71	$808.70	$808.70