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	$190.29	8.141%	$205.7815	$205.78	$205.80	$205.80
Purchase #2	$106.30	13.472%	$120.6207	$120.62	$120.60	$120.60
Purchase #3	$136.28	10.653%	$150.7979	$150.80	$150.80	$150.80
Purchase #4	$46.77	10.247%	$51.5625	$51.56	$51.55	$51.60
Purchase #5	$32.96	13.343%	$37.3579	$37.36	$37.35	$37.40
Purchase #6	$115.47	4.288%	$120.4214	$120.42	$120.40	$120.40
Purchase #7	$240.47	6.460%	$256.0044	$256.00	$256.00	$256.00
7 purchase totals =	$868.54		$942.5463	$942.54	$942.50	$942.60