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	$168.62	4.242%	$175.7729	$175.77	$175.75	$175.80
Purchase #2	$191.25	7.540%	$205.6703	$205.67	$205.65	$205.70
Purchase #3	$84.28	10.743%	$93.3342	$93.33	$93.35	$93.30
Purchase #4	$30.46	8.384%	$33.0138	$33.01	$33.00	$33.00
Purchase #5	$160.33	3.102%	$165.3034	$165.30	$165.30	$165.30
Purchase #6	$72.97	13.599%	$82.8932	$82.89	$82.90	$82.90
Purchase #7	$55.25	7.609%	$59.454	$59.45	$59.45	$59.50
7 purchase totals =	$763.16		$815.4418	$815.42	$815.40	$815.50