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	$183.88	10.669%	$203.4982	$203.50	$203.50	$203.50
Purchase #2	$236.56	7.198%	$253.5876	$253.59	$253.60	$253.60
Purchase #3	$43.71	4.152%	$45.5248	$45.52	$45.50	$45.50
Purchase #4	$126.62	4.365%	$132.147	$132.15	$132.15	$132.10
Purchase #5	$178.89	5.818%	$189.2978	$189.30	$189.30	$189.30
Purchase #6	$146.84	10.508%	$162.2699	$162.27	$162.25	$162.30
Purchase #7	$35.73	6.109%	$37.9127	$37.91	$37.90	$37.90
7 purchase totals =	$952.23		$1,024.2380	$1,024.24	$1,024.20	$1,024.20