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	$191.82	10.603%	$212.1587	$212.16	$212.15	$212.20
Purchase #2	$156.90	5.504%	$165.5358	$165.54	$165.55	$165.50
Purchase #3	$164.67	6.247%	$174.9569	$174.96	$174.95	$175.00
Purchase #4	$248.52	13.503%	$282.0777	$282.08	$282.10	$282.10
Purchase #5	$16.83	5.739%	$17.7959	$17.80	$17.80	$17.80
Purchase #6	$106.93	4.120%	$111.3355	$111.34	$111.35	$111.30
Purchase #7	$131.44	4.221%	$136.9881	$136.99	$137.00	$137.00
7 purchase totals =	$1,017.11		$1,100.8486	$1,100.87	$1,100.90	$1,100.90