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	$65.93	11.224%	$73.33	$73.33	$73.35	$73.30
Purchase #2	$60.48	13.232%	$68.4827	$68.48	$68.50	$68.50
Purchase #3	$69.94	13.871%	$79.6414	$79.64	$79.65	$79.60
Purchase #4	$204.64	8.777%	$222.6013	$222.60	$222.60	$222.60
Purchase #5	$55.76	12.289%	$62.6123	$62.61	$62.60	$62.60
Purchase #6	$228.43	5.541%	$241.0873	$241.09	$241.10	$241.10
Purchase #7	$243.71	10.739%	$269.882	$269.88	$269.90	$269.90
7 purchase totals =	$928.89		$1,017.6370	$1,017.63	$1,017.70	$1,017.60