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	$151.36	6.254%	$160.8261	$160.83	$160.85	$160.80
Purchase #2	$171.42	11.554%	$191.2259	$191.23	$191.25	$191.20
Purchase #3	$143.54	4.619%	$150.1701	$150.17	$150.15	$150.20
Purchase #4	$191.55	4.639%	$200.436	$200.44	$200.45	$200.40
Purchase #5	$158.65	9.771%	$174.1517	$174.15	$174.15	$174.20
Purchase #6	$55.47	3.439%	$57.3776	$57.38	$57.40	$57.40
Purchase #7	$31.47	12.297%	$35.3399	$35.34	$35.35	$35.30
7 purchase totals =	$903.46		$969.5273	$969.54	$969.60	$969.50