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	$64.33	13.867%	$73.2506	$73.25	$73.25	$73.30
Purchase #2	$241.35	13.199%	$273.2058	$273.21	$273.20	$273.20
Purchase #3	$214.67	3.561%	$222.3144	$222.31	$222.30	$222.30
Purchase #4	$151.57	8.724%	$164.793	$164.79	$164.80	$164.80
Purchase #5	$98.64	7.849%	$106.3823	$106.38	$106.40	$106.40
Purchase #6	$159.50	5.650%	$168.5118	$168.51	$168.50	$168.50
Purchase #7	$67.59	12.692%	$76.1685	$76.17	$76.15	$76.20
7 purchase totals =	$997.65		$1,084.6264	$1,084.62	$1,084.60	$1,084.70