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	$115.89	6.348%	$123.2467	$123.25	$123.25	$123.20
Purchase #2	$186.97	4.607%	$195.5837	$195.58	$195.60	$195.60
Purchase #3	$219.92	4.489%	$229.7922	$229.79	$229.80	$229.80
Purchase #4	$49.55	10.687%	$54.8454	$54.85	$54.85	$54.80
Purchase #5	$175.58	8.490%	$190.4867	$190.49	$190.50	$190.50
Purchase #6	$69.97	12.436%	$78.6715	$78.67	$78.65	$78.70
Purchase #7	$245.90	6.532%	$261.9622	$261.96	$261.95	$262.00
7 purchase totals =	$1,063.78		$1,134.5884	$1,134.59	$1,134.60	$1,134.60