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	$85.83	10.169%	$94.5581	$94.56	$94.55	$94.60
Purchase #2	$169.47	11.298%	$188.6167	$188.62	$188.60	$188.60
Purchase #3	$191.76	5.544%	$202.3912	$202.39	$202.40	$202.40
Purchase #4	$123.89	8.383%	$134.2757	$134.28	$134.30	$134.30
Purchase #5	$83.65	5.769%	$88.4758	$88.48	$88.50	$88.50
Purchase #6	$154.53	8.381%	$167.4812	$167.48	$167.50	$167.50
Purchase #7	$145.79	6.538%	$155.3218	$155.32	$155.30	$155.30
7 purchase totals =	$954.92		$1,031.1205	$1,031.13	$1,031.15	$1,031.20