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	$181.49	11.453%	$202.276	$202.28	$202.30	$202.30
Purchase #2	$88.87	13.801%	$101.1349	$101.13	$101.15	$101.10
Purchase #3	$61.82	4.632%	$64.6835	$64.68	$64.70	$64.70
Purchase #4	$86.98	5.208%	$91.5099	$91.51	$91.50	$91.50
Purchase #5	$190.71	5.141%	$200.5144	$200.51	$200.50	$200.50
Purchase #6	$154.82	4.765%	$162.1972	$162.20	$162.20	$162.20
Purchase #7	$128.56	10.383%	$141.9084	$141.91	$141.90	$141.90
7 purchase totals =	$893.25		$964.2243	$964.22	$964.25	$964.20