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	$56.60	5.670%	$59.8092	$59.81	$59.80	$59.80
Purchase #2	$184.36	3.245%	$190.3425	$190.34	$190.35	$190.30
Purchase #3	$20.84	3.138%	$21.494	$21.49	$21.50	$21.50
Purchase #4	$48.62	13.144%	$55.0106	$55.01	$55.00	$55.00
Purchase #5	$200.59	11.836%	$224.3318	$224.33	$224.35	$224.30
Purchase #6	$111.62	12.123%	$125.1517	$125.15	$125.15	$125.20
Purchase #7	$125.73	12.589%	$141.5581	$141.56	$141.55	$141.60
7 purchase totals =	$748.36		$817.6979	$817.69	$817.70	$817.70