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	$238.83	11.479%	$266.2453	$266.25	$266.25	$266.20
Purchase #2	$54.98	7.446%	$59.0738	$59.07	$59.05	$59.10
Purchase #3	$81.40	11.813%	$91.0158	$91.02	$91.00	$91.00
Purchase #4	$137.91	3.532%	$142.781	$142.78	$142.80	$142.80
Purchase #5	$78.50	4.309%	$81.8826	$81.88	$81.90	$81.90
Purchase #6	$28.60	4.341%	$29.8415	$29.84	$29.85	$29.80
Purchase #7	$243.80	13.841%	$277.5444	$277.54	$277.55	$277.50
7 purchase totals =	$864.02		$948.3844	$948.38	$948.40	$948.30