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	$9.41	12.532%	$10.5893	$10.59	$10.60	$10.60
Purchase #2	$88.76	3.235%	$91.6314	$91.63	$91.65	$91.60
Purchase #3	$29.48	6.315%	$31.3417	$31.34	$31.35	$31.30
Purchase #4	$29.25	13.339%	$33.1517	$33.15	$33.15	$33.20
Purchase #5	$37.85	9.701%	$41.5218	$41.52	$41.50	$41.50
Purchase #6	$73.67	8.345%	$79.8178	$79.82	$79.80	$79.80
Purchase #7	$146.48	13.550%	$166.328	$166.33	$166.35	$166.30
7 purchase totals =	$414.90		$454.3817	$454.38	$454.40	$454.30