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	$61.87	5.174%	$65.0712	$65.07	$65.05	$65.10
Purchase #2	$37.86	9.239%	$41.3579	$41.36	$41.35	$41.40
Purchase #3	$92.30	3.104%	$95.165	$95.17	$95.15	$95.20
Purchase #4	$200.88	7.693%	$216.3337	$216.33	$216.35	$216.30
Purchase #5	$220.91	9.815%	$242.5923	$242.59	$242.60	$242.60
Purchase #6	$161.41	12.190%	$181.0859	$181.09	$181.10	$181.10
Purchase #7	$117.36	5.238%	$123.5073	$123.51	$123.50	$123.50
7 purchase totals =	$892.59		$965.1133	$965.12	$965.10	$965.20