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	$113.43	12.609%	$127.7324	$127.73	$127.75	$127.70
Purchase #2	$154.94	9.320%	$169.3804	$169.38	$169.40	$169.40
Purchase #3	$99.67	4.464%	$104.1193	$104.12	$104.10	$104.10
Purchase #4	$190.29	10.442%	$210.1601	$210.16	$210.15	$210.20
Purchase #5	$115.66	9.207%	$126.3088	$126.31	$126.30	$126.30
Purchase #6	$227.30	11.461%	$253.3509	$253.35	$253.35	$253.40
Purchase #7	$88.42	12.517%	$99.4875	$99.49	$99.50	$99.50
7 purchase totals =	$989.71		$1,090.5394	$1,090.54	$1,090.55	$1,090.60