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	$203.82	4.753%	$213.5076	$213.51	$213.50	$213.50
Purchase #2	$70.94	10.666%	$78.5065	$78.51	$78.50	$78.50
Purchase #3	$108.61	4.561%	$113.5637	$113.56	$113.55	$113.60
Purchase #4	$155.51	11.809%	$173.8742	$173.87	$173.85	$173.90
Purchase #5	$80.93	12.307%	$90.8901	$90.89	$90.90	$90.90
Purchase #6	$214.78	3.783%	$222.9051	$222.91	$222.90	$222.90
Purchase #7	$115.97	3.743%	$120.3108	$120.31	$120.30	$120.30
7 purchase totals =	$950.56		$1,013.5580	$1,013.56	$1,013.50	$1,013.60