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	$215.36	10.792%	$238.6017	$238.60	$238.60	$238.60
Purchase #2	$93.85	6.754%	$100.1886	$100.19	$100.20	$100.20
Purchase #3	$191.80	8.856%	$208.7858	$208.79	$208.80	$208.80
Purchase #4	$226.91	5.150%	$238.5959	$238.60	$238.60	$238.60
Purchase #5	$164.91	4.211%	$171.8544	$171.85	$171.85	$171.90
Purchase #6	$58.65	4.285%	$61.1632	$61.16	$61.15	$61.20
Purchase #7	$182.98	3.785%	$189.9058	$189.91	$189.90	$189.90
7 purchase totals =	$1,134.46		$1,209.0954	$1,209.10	$1,209.10	$1,209.20