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	$237.97	10.203%	$262.2501	$262.25	$262.25	$262.30
Purchase #2	$219.93	12.611%	$247.6654	$247.67	$247.65	$247.70
Purchase #3	$154.89	11.702%	$173.0152	$173.02	$173.00	$173.00
Purchase #4	$243.45	12.308%	$273.4138	$273.41	$273.40	$273.40
Purchase #5	$78.52	8.765%	$85.4023	$85.40	$85.40	$85.40
Purchase #6	$40.43	11.402%	$45.0398	$45.04	$45.05	$45.00
Purchase #7	$26.27	9.760%	$28.834	$28.83	$28.85	$28.80
7 purchase totals =	$1,001.46		$1,115.6206	$1,115.62	$1,115.60	$1,115.60