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	$81.95	12.390%	$92.1036	$92.10	$92.10	$92.10
Purchase #2	$206.45	7.532%	$221.9998	$222.00	$222.00	$222.00
Purchase #3	$166.46	10.297%	$183.6004	$183.60	$183.60	$183.60
Purchase #4	$245.37	4.692%	$256.8828	$256.88	$256.90	$256.90
Purchase #5	$45.49	10.703%	$50.3588	$50.36	$50.35	$50.40
Purchase #6	$171.86	10.206%	$189.4	$189.40	$189.40	$189.40
Purchase #7	$192.96	12.218%	$216.5359	$216.54	$216.55	$216.50
7 purchase totals =	$1,110.54		$1,210.8813	$1,210.88	$1,210.90	$1,210.90