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	$148.32	11.342%	$165.1425	$165.14	$165.15	$165.10
Purchase #2	$49.54	13.361%	$56.159	$56.16	$56.15	$56.20
Purchase #3	$130.93	9.748%	$143.6931	$143.69	$143.70	$143.70
Purchase #4	$222.86	9.137%	$243.2227	$243.22	$243.20	$243.20
Purchase #5	$31.83	10.269%	$35.0986	$35.10	$35.10	$35.10
Purchase #6	$64.50	12.366%	$72.4761	$72.48	$72.50	$72.50
Purchase #7	$137.37	9.339%	$150.199	$150.20	$150.20	$150.20
7 purchase totals =	$785.35		$865.9910	$865.99	$866.00	$866.00