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	$84.33	10.133%	$92.8752	$92.88	$92.90	$92.90
Purchase #2	$75.28	11.489%	$83.9289	$83.93	$83.95	$83.90
Purchase #3	$248.62	10.860%	$275.6201	$275.62	$275.60	$275.60
Purchase #4	$53.44	10.827%	$59.2259	$59.23	$59.25	$59.20
Purchase #5	$22.64	7.734%	$24.391	$24.39	$24.40	$24.40
Purchase #6	$172.38	4.482%	$180.1061	$180.11	$180.10	$180.10
Purchase #7	$218.32	6.166%	$231.7816	$231.78	$231.80	$231.80
7 purchase totals =	$875.01		$947.9288	$947.94	$948.00	$947.90