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	$14.33	3.775%	$14.871	$14.87	$14.85	$14.90
Purchase #2	$89.74	8.429%	$97.3042	$97.30	$97.30	$97.30
Purchase #3	$53.51	3.104%	$55.171	$55.17	$55.15	$55.20
Purchase #4	$227.95	6.604%	$243.0038	$243.00	$243.00	$243.00
Purchase #5	$18.81	10.222%	$20.7328	$20.73	$20.75	$20.70
Purchase #6	$63.55	13.590%	$72.1864	$72.19	$72.20	$72.20
Purchase #7	$30.28	4.168%	$31.5421	$31.54	$31.55	$31.50
7 purchase totals =	$498.17		$534.8113	$534.80	$534.80	$534.80