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	$101.82	9.377%	$111.3677	$111.37	$111.35	$111.40
Purchase #2	$172.87	3.209%	$178.4174	$178.42	$178.40	$178.40
Purchase #3	$245.30	11.222%	$272.8276	$272.83	$272.85	$272.80
Purchase #4	$148.31	11.240%	$164.98	$164.98	$165.00	$165.00
Purchase #5	$108.84	6.694%	$116.1257	$116.13	$116.15	$116.10
Purchase #6	$227.71	10.137%	$250.793	$250.79	$250.80	$250.80
Purchase #7	$71.48	9.724%	$78.4307	$78.43	$78.45	$78.40
7 purchase totals =	$1,076.33		$1,172.9421	$1,172.95	$1,173.00	$1,172.90