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	$75.97	3.580%	$78.6897	$78.69	$78.70	$78.70
Purchase #2	$150.78	6.483%	$160.5551	$160.56	$160.55	$160.60
Purchase #3	$71.80	6.548%	$76.5015	$76.50	$76.50	$76.50
Purchase #4	$189.46	13.710%	$215.435	$215.44	$215.45	$215.40
Purchase #5	$34.80	6.547%	$37.0784	$37.08	$37.10	$37.10
Purchase #6	$239.52	10.173%	$263.8864	$263.89	$263.90	$263.90
Purchase #7	$164.52	7.115%	$176.2256	$176.23	$176.25	$176.20
7 purchase totals =	$926.85		$1,008.3717	$1,008.39	$1,008.45	$1,008.40