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	$79.31	3.376%	$81.9875	$81.99	$82.00	$82.00
Purchase #2	$48.94	3.223%	$50.5173	$50.52	$50.50	$50.50
Purchase #3	$218.73	11.375%	$243.6105	$243.61	$243.60	$243.60
Purchase #4	$26.50	5.166%	$27.869	$27.87	$27.85	$27.90
Purchase #5	$56.81	5.510%	$59.9402	$59.94	$59.95	$59.90
Purchase #6	$66.56	9.745%	$73.0463	$73.05	$73.05	$73.00
Purchase #7	$190.41	11.837%	$212.9488	$212.95	$212.95	$212.90
7 purchase totals =	$687.26		$749.9196	$749.93	$749.90	$749.80