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	$116.52	4.844%	$122.1642	$122.16	$122.15	$122.20
Purchase #2	$169.68	11.349%	$188.937	$188.94	$188.95	$188.90
Purchase #3	$86.82	9.306%	$94.8995	$94.90	$94.90	$94.90
Purchase #4	$90.47	10.291%	$99.7803	$99.78	$99.80	$99.80
Purchase #5	$139.75	5.190%	$147.003	$147.00	$147.00	$147.00
Purchase #6	$140.84	10.722%	$155.9409	$155.94	$155.95	$155.90
Purchase #7	$127.75	11.595%	$142.5626	$142.56	$142.55	$142.60
7 purchase totals =	$871.83		$951.2875	$951.28	$951.30	$951.30