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	$94.87	10.192%	$104.5392	$104.54	$104.55	$104.50
Purchase #2	$89.68	11.818%	$100.2784	$100.28	$100.30	$100.30
Purchase #3	$80.50	13.773%	$91.5873	$91.59	$91.60	$91.60
Purchase #4	$227.46	5.461%	$239.8816	$239.88	$239.90	$239.90
Purchase #5	$39.58	6.266%	$42.0601	$42.06	$42.05	$42.10
Purchase #6	$87.90	13.496%	$99.763	$99.76	$99.75	$99.80
Purchase #7	$109.91	13.277%	$124.5028	$124.50	$124.50	$124.50
7 purchase totals =	$729.90		$802.6124	$802.61	$802.65	$802.70