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	$141.36	10.761%	$156.5717	$156.57	$156.55	$156.60
Purchase #2	$201.74	6.419%	$214.6897	$214.69	$214.70	$214.70
Purchase #3	$19.25	5.219%	$20.2547	$20.25	$20.25	$20.30
Purchase #4	$57.38	7.648%	$61.7684	$61.77	$61.75	$61.80
Purchase #5	$10.40	10.523%	$11.4944	$11.49	$11.50	$11.50
Purchase #6	$86.62	3.744%	$89.8631	$89.86	$89.85	$89.90
Purchase #7	$55.57	10.353%	$61.3232	$61.32	$61.30	$61.30
7 purchase totals =	$572.32		$615.9652	$615.95	$615.90	$616.10