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	$182.25	10.160%	$200.7666	$200.77	$200.75	$200.80
Purchase #2	$183.81	6.746%	$196.2098	$196.21	$196.20	$196.20
Purchase #3	$14.92	5.201%	$15.696	$15.70	$15.70	$15.70
Purchase #4	$191.26	11.800%	$213.8287	$213.83	$213.85	$213.80
Purchase #5	$105.85	4.656%	$110.7784	$110.78	$110.80	$110.80
Purchase #6	$70.91	7.599%	$76.2985	$76.30	$76.30	$76.30
Purchase #7	$33.60	12.437%	$37.7788	$37.78	$37.80	$37.80
7 purchase totals =	$782.60		$851.3568	$851.37	$851.40	$851.40