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	$181.92	5.431%	$191.8001	$191.80	$191.80	$191.80
Purchase #2	$113.46	8.622%	$123.2425	$123.24	$123.25	$123.20
Purchase #3	$175.77	5.325%	$185.1298	$185.13	$185.15	$185.10
Purchase #4	$118.42	7.615%	$127.4377	$127.44	$127.45	$127.40
Purchase #5	$234.49	13.404%	$265.921	$265.92	$265.90	$265.90
Purchase #6	$87.60	12.413%	$98.4738	$98.47	$98.45	$98.50
Purchase #7	$45.99	7.260%	$49.3289	$49.33	$49.35	$49.30
7 purchase totals =	$957.65		$1,041.3338	$1,041.33	$1,041.35	$1,041.20