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	$6.98	4.282%	$7.2789	$7.28	$7.30	$7.30
Purchase #2	$210.77	13.757%	$239.7656	$239.77	$239.75	$239.80
Purchase #3	$244.26	7.256%	$261.9835	$261.98	$262.00	$262.00
Purchase #4	$102.45	6.770%	$109.3859	$109.39	$109.40	$109.40
Purchase #5	$115.84	13.441%	$131.4101	$131.41	$131.40	$131.40
Purchase #6	$239.46	6.820%	$255.7912	$255.79	$255.80	$255.80
Purchase #7	$131.39	6.850%	$140.3902	$140.39	$140.40	$140.40
7 purchase totals =	$1,051.15		$1,146.0054	$1,146.01	$1,146.05	$1,146.10