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	$216.78	11.781%	$242.3189	$242.32	$242.30	$242.30
Purchase #2	$134.67	7.369%	$144.5938	$144.59	$144.60	$144.60
Purchase #3	$124.57	13.638%	$141.5589	$141.56	$141.55	$141.60
Purchase #4	$207.61	11.377%	$231.2298	$231.23	$231.25	$231.20
Purchase #5	$97.64	11.136%	$108.5132	$108.51	$108.50	$108.50
Purchase #6	$201.29	13.173%	$227.8059	$227.81	$227.80	$227.80
Purchase #7	$69.44	11.117%	$77.1596	$77.16	$77.15	$77.20
7 purchase totals =	$1,052.00		$1,173.1801	$1,173.18	$1,173.15	$1,173.20