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	$85.95	6.391%	$91.4431	$91.44	$91.45	$91.40
Purchase #2	$222.62	10.160%	$245.2382	$245.24	$245.25	$245.20
Purchase #3	$216.31	4.303%	$225.6178	$225.62	$225.60	$225.60
Purchase #4	$46.28	8.344%	$50.1416	$50.14	$50.15	$50.10
Purchase #5	$25.72	11.348%	$28.6387	$28.64	$28.65	$28.60
Purchase #6	$83.27	9.770%	$91.4055	$91.41	$91.40	$91.40
Purchase #7	$123.72	6.361%	$131.5898	$131.59	$131.60	$131.60
7 purchase totals =	$803.87		$864.0747	$864.08	$864.10	$863.90