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	$161.38	6.753%	$172.278	$172.28	$172.30	$172.30
Purchase #2	$194.73	8.205%	$210.7076	$210.71	$210.70	$210.70
Purchase #3	$133.69	7.302%	$143.452	$143.45	$143.45	$143.50
Purchase #4	$57.68	8.833%	$62.7749	$62.77	$62.75	$62.80
Purchase #5	$29.26	12.414%	$32.8923	$32.89	$32.90	$32.90
Purchase #6	$232.37	13.499%	$263.7376	$263.74	$263.75	$263.70
Purchase #7	$160.48	7.786%	$172.975	$172.98	$173.00	$173.00
7 purchase totals =	$969.59		$1,058.8174	$1,058.82	$1,058.85	$1,058.90