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	$33.50	12.646%	$37.7364	$37.74	$37.75	$37.70
Purchase #2	$134.36	6.150%	$142.6231	$142.62	$142.60	$142.60
Purchase #3	$208.26	7.520%	$223.9212	$223.92	$223.90	$223.90
Purchase #4	$160.60	8.664%	$174.5144	$174.51	$174.50	$174.50
Purchase #5	$91.92	3.364%	$95.0122	$95.01	$95.00	$95.00
Purchase #6	$228.69	7.741%	$246.3929	$246.39	$246.40	$246.40
Purchase #7	$223.92	8.190%	$242.259	$242.26	$242.25	$242.30
7 purchase totals =	$1,081.25		$1,162.4592	$1,162.45	$1,162.40	$1,162.40