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	$70.61	7.756%	$76.0865	$76.09	$76.10	$76.10
Purchase #2	$171.28	11.195%	$190.4548	$190.45	$190.45	$190.50
Purchase #3	$153.83	7.220%	$164.9365	$164.94	$164.95	$164.90
Purchase #4	$71.65	11.650%	$79.9972	$80.00	$80.00	$80.00
Purchase #5	$55.67	6.539%	$59.3103	$59.31	$59.30	$59.30
Purchase #6	$248.55	11.268%	$276.5566	$276.56	$276.55	$276.60
Purchase #7	$241.50	12.198%	$270.9582	$270.96	$270.95	$271.00
7 purchase totals =	$1,013.09		$1,118.3001	$1,118.31	$1,118.30	$1,118.40