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	$177.30	7.224%	$190.1082	$190.11	$190.10	$190.10
Purchase #2	$102.57	13.459%	$116.3749	$116.37	$116.35	$116.40
Purchase #3	$152.85	8.173%	$165.3424	$165.34	$165.35	$165.30
Purchase #4	$80.71	7.726%	$86.9457	$86.95	$86.95	$86.90
Purchase #5	$35.43	13.721%	$40.2914	$40.29	$40.30	$40.30
Purchase #6	$240.74	6.583%	$256.5879	$256.59	$256.60	$256.60
Purchase #7	$90.92	6.427%	$96.7634	$96.76	$96.75	$96.80
7 purchase totals =	$880.52		$952.4139	$952.41	$952.40	$952.40