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	$102.49	9.581%	$112.3096	$112.31	$112.30	$112.30
Purchase #2	$39.58	13.244%	$44.822	$44.82	$44.80	$44.80
Purchase #3	$25.60	6.160%	$27.177	$27.18	$27.20	$27.20
Purchase #4	$139.73	5.184%	$146.9736	$146.97	$146.95	$147.00
Purchase #5	$174.41	12.710%	$196.5775	$196.58	$196.60	$196.60
Purchase #6	$54.39	13.173%	$61.5548	$61.55	$61.55	$61.60
Purchase #7	$135.94	4.591%	$142.181	$142.18	$142.20	$142.20
7 purchase totals =	$672.14		$731.5955	$731.59	$731.60	$731.70