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	$56.61	10.350%	$62.4691	$62.47	$62.45	$62.50
Purchase #2	$143.37	4.838%	$150.3062	$150.31	$150.30	$150.30
Purchase #3	$125.35	4.854%	$131.4345	$131.43	$131.45	$131.40
Purchase #4	$80.97	10.803%	$89.7172	$89.72	$89.70	$89.70
Purchase #5	$57.79	11.560%	$64.4705	$64.47	$64.45	$64.50
Purchase #6	$33.59	7.121%	$35.9819	$35.98	$36.00	$36.00
Purchase #7	$164.54	3.753%	$170.7152	$170.72	$170.70	$170.70
7 purchase totals =	$662.22		$705.0946	$705.10	$705.05	$705.10