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	$114.94	10.475%	$126.98	$126.98	$127.00	$127.00
Purchase #2	$160.77	12.499%	$180.8646	$180.86	$180.85	$180.90
Purchase #3	$157.73	13.721%	$179.3721	$179.37	$179.35	$179.40
Purchase #4	$78.41	12.773%	$88.4253	$88.43	$88.45	$88.40
Purchase #5	$24.82	13.744%	$28.2313	$28.23	$28.25	$28.20
Purchase #6	$205.26	4.818%	$215.1494	$215.15	$215.15	$215.10
Purchase #7	$188.86	8.854%	$205.5817	$205.58	$205.60	$205.60
7 purchase totals =	$930.79		$1,024.6044	$1,024.60	$1,024.65	$1,024.60