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	$119.48	10.485%	$132.0075	$132.01	$132.00	$132.00
Purchase #2	$69.38	5.439%	$73.1536	$73.15	$73.15	$73.20
Purchase #3	$80.94	10.254%	$89.2396	$89.24	$89.25	$89.20
Purchase #4	$11.76	9.397%	$12.8651	$12.87	$12.85	$12.90
Purchase #5	$40.31	5.678%	$42.5988	$42.60	$42.60	$42.60
Purchase #6	$123.85	9.574%	$135.7074	$135.71	$135.70	$135.70
Purchase #7	$196.89	8.491%	$213.6079	$213.61	$213.60	$213.60
7 purchase totals =	$642.61		$699.1799	$699.19	$699.15	$699.20