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	$177.30	4.781%	$185.7767	$185.78	$185.80	$185.80
Purchase #2	$160.40	4.112%	$166.9956	$167.00	$167.00	$167.00
Purchase #3	$196.85	6.118%	$208.8933	$208.89	$208.90	$208.90
Purchase #4	$52.94	9.305%	$57.8661	$57.87	$57.85	$57.90
Purchase #5	$106.56	11.614%	$118.9359	$118.94	$118.95	$118.90
Purchase #6	$49.88	7.249%	$53.4958	$53.50	$53.50	$53.50
Purchase #7	$95.72	5.321%	$100.8133	$100.81	$100.80	$100.80
7 purchase totals =	$839.65		$892.7767	$892.79	$892.80	$892.80