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	$161.89	10.314%	$178.5873	$178.59	$178.60	$178.60
Purchase #2	$160.60	13.544%	$182.3517	$182.35	$182.35	$182.40
Purchase #3	$103.48	7.462%	$111.2017	$111.20	$111.20	$111.20
Purchase #4	$88.59	10.674%	$98.0461	$98.05	$98.05	$98.00
Purchase #5	$212.57	13.700%	$241.6921	$241.69	$241.70	$241.70
Purchase #6	$45.56	7.335%	$48.9018	$48.90	$48.90	$48.90
Purchase #7	$96.98	7.592%	$104.3427	$104.34	$104.35	$104.30
7 purchase totals =	$869.67		$965.1234	$965.12	$965.15	$965.10