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	$241.59	13.365%	$273.8785	$273.88	$273.90	$273.90
Purchase #2	$155.60	6.117%	$165.1181	$165.12	$165.10	$165.10
Purchase #3	$205.96	5.252%	$216.777	$216.78	$216.80	$216.80
Purchase #4	$230.91	3.331%	$238.6016	$238.60	$238.60	$238.60
Purchase #5	$72.52	11.477%	$80.8431	$80.84	$80.85	$80.80
Purchase #6	$249.28	10.471%	$275.3821	$275.38	$275.40	$275.40
Purchase #7	$101.90	3.832%	$105.8048	$105.80	$105.80	$105.80
7 purchase totals =	$1,257.76		$1,356.4052	$1,356.40	$1,356.45	$1,356.40