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	$156.39	9.807%	$171.7272	$171.73	$171.75	$171.70
Purchase #2	$18.70	10.543%	$20.6715	$20.67	$20.65	$20.70
Purchase #3	$59.52	11.781%	$66.5321	$66.53	$66.55	$66.50
Purchase #4	$128.65	13.856%	$146.4757	$146.48	$146.50	$146.50
Purchase #5	$168.55	4.642%	$176.3741	$176.37	$176.35	$176.40
Purchase #6	$64.69	10.759%	$71.65	$71.65	$71.65	$71.70
Purchase #7	$114.99	3.137%	$118.5972	$118.60	$118.60	$118.60
7 purchase totals =	$711.49		$772.0278	$772.03	$772.05	$772.10