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	$214.60	11.172%	$238.5751	$238.58	$238.60	$238.60
Purchase #2	$93.98	5.667%	$99.3058	$99.31	$99.30	$99.30
Purchase #3	$147.52	9.650%	$161.7557	$161.76	$161.75	$161.80
Purchase #4	$180.34	4.170%	$187.8602	$187.86	$187.85	$187.90
Purchase #5	$217.25	7.420%	$233.37	$233.37	$233.35	$233.40
Purchase #6	$97.57	3.398%	$100.8854	$100.89	$100.90	$100.90
Purchase #7	$152.34	11.765%	$170.2628	$170.26	$170.25	$170.30
7 purchase totals =	$1,103.60		$1,192.0150	$1,192.03	$1,192.00	$1,192.20