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	$94.32	6.618%	$100.5621	$100.56	$100.55	$100.60
Purchase #2	$100.39	9.152%	$109.5777	$109.58	$109.60	$109.60
Purchase #3	$205.64	7.131%	$220.3042	$220.30	$220.30	$220.30
Purchase #4	$163.33	5.829%	$172.8505	$172.85	$172.85	$172.90
Purchase #5	$216.83	12.793%	$244.5691	$244.57	$244.55	$244.60
Purchase #6	$156.51	12.694%	$176.3774	$176.38	$176.40	$176.40
Purchase #7	$140.28	5.643%	$148.196	$148.20	$148.20	$148.20
7 purchase totals =	$1,077.30		$1,172.4370	$1,172.44	$1,172.45	$1,172.60