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	$236.44	9.150%	$258.0743	$258.07	$258.05	$258.10
Purchase #2	$64.92	4.512%	$67.8492	$67.85	$67.85	$67.80
Purchase #3	$176.62	13.669%	$200.7622	$200.76	$200.75	$200.80
Purchase #4	$142.47	6.724%	$152.0497	$152.05	$152.05	$152.00
Purchase #5	$78.34	9.669%	$85.9147	$85.91	$85.90	$85.90
Purchase #6	$123.81	3.193%	$127.7633	$127.76	$127.75	$127.80
Purchase #7	$188.67	8.127%	$204.0032	$204.00	$204.00	$204.00
7 purchase totals =	$1,011.27		$1,096.4166	$1,096.40	$1,096.35	$1,096.40