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	$143.67	4.633%	$150.3262	$150.33	$150.35	$150.30
Purchase #2	$79.30	8.421%	$85.9779	$85.98	$86.00	$86.00
Purchase #3	$172.44	10.623%	$190.7583	$190.76	$190.75	$190.80
Purchase #4	$10.31	4.357%	$10.7592	$10.76	$10.75	$10.80
Purchase #5	$216.45	9.856%	$237.7833	$237.78	$237.80	$237.80
Purchase #6	$9.78	7.470%	$10.5106	$10.51	$10.50	$10.50
Purchase #7	$53.53	8.164%	$57.9002	$57.90	$57.90	$57.90
7 purchase totals =	$685.48		$744.0157	$744.02	$744.05	$744.10