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	$146.94	10.457%	$162.3055	$162.31	$162.30	$162.30
Purchase #2	$204.33	12.762%	$230.4066	$230.41	$230.40	$230.40
Purchase #3	$165.65	9.198%	$180.8865	$180.89	$180.90	$180.90
Purchase #4	$246.85	4.581%	$258.1582	$258.16	$258.15	$258.20
Purchase #5	$167.60	4.172%	$174.5923	$174.59	$174.60	$174.60
Purchase #6	$137.65	9.402%	$150.5919	$150.59	$150.60	$150.60
Purchase #7	$188.63	5.452%	$198.9141	$198.91	$198.90	$198.90
7 purchase totals =	$1,257.65		$1,355.8551	$1,355.86	$1,355.85	$1,355.90