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	$174.32	13.866%	$198.4912	$198.49	$198.50	$198.50
Purchase #2	$187.77	8.869%	$204.4233	$204.42	$204.40	$204.40
Purchase #3	$208.33	4.406%	$217.509	$217.51	$217.50	$217.50
Purchase #4	$135.78	8.213%	$146.9316	$146.93	$146.95	$146.90
Purchase #5	$92.41	6.219%	$98.157	$98.16	$98.15	$98.20
Purchase #6	$76.77	6.868%	$82.0426	$82.04	$82.05	$82.00
Purchase #7	$149.53	9.838%	$164.2408	$164.24	$164.25	$164.20
7 purchase totals =	$1,024.91		$1,111.7955	$1,111.79	$1,111.80	$1,111.70