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	$175.56	12.173%	$196.9309	$196.93	$196.95	$196.90
Purchase #2	$188.85	7.728%	$203.4443	$203.44	$203.45	$203.40
Purchase #3	$103.79	11.814%	$116.0518	$116.05	$116.05	$116.10
Purchase #4	$217.64	5.415%	$229.4252	$229.43	$229.45	$229.40
Purchase #5	$169.29	13.404%	$191.9816	$191.98	$192.00	$192.00
Purchase #6	$229.35	11.505%	$255.7367	$255.74	$255.75	$255.70
Purchase #7	$81.93	4.726%	$85.802	$85.80	$85.80	$85.80
7 purchase totals =	$1,166.41		$1,279.3725	$1,279.37	$1,279.45	$1,279.30