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	$170.56	11.559%	$190.275	$190.28	$190.30	$190.30
Purchase #2	$77.77	5.377%	$81.9517	$81.95	$81.95	$82.00
Purchase #3	$208.98	13.838%	$237.8987	$237.90	$237.90	$237.90
Purchase #4	$20.79	6.596%	$22.1613	$22.16	$22.15	$22.20
Purchase #5	$173.40	8.600%	$188.3124	$188.31	$188.30	$188.30
Purchase #6	$134.46	7.663%	$144.7637	$144.76	$144.75	$144.80
Purchase #7	$156.71	5.796%	$165.7929	$165.79	$165.80	$165.80
7 purchase totals =	$942.67		$1,031.1557	$1,031.15	$1,031.15	$1,031.30