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	$66.92	5.358%	$70.5056	$70.51	$70.50	$70.50
Purchase #2	$170.90	6.370%	$181.7863	$181.79	$181.80	$181.80
Purchase #3	$207.94	6.319%	$221.0797	$221.08	$221.10	$221.10
Purchase #4	$89.54	5.370%	$94.3483	$94.35	$94.35	$94.30
Purchase #5	$242.56	5.376%	$255.6	$255.60	$255.60	$255.60
Purchase #6	$73.49	6.399%	$78.1926	$78.19	$78.20	$78.20
Purchase #7	$153.90	10.466%	$170.0072	$170.01	$170.00	$170.00
7 purchase totals =	$1,005.25		$1,071.5197	$1,071.53	$1,071.55	$1,071.50