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	$83.75	4.110%	$87.1921	$87.19	$87.20	$87.20
Purchase #2	$120.33	5.254%	$126.6521	$126.65	$126.65	$126.70
Purchase #3	$230.57	10.808%	$255.49	$255.49	$255.50	$255.50
Purchase #4	$190.82	13.412%	$216.4128	$216.41	$216.40	$216.40
Purchase #5	$46.78	9.321%	$51.1404	$51.14	$51.15	$51.10
Purchase #6	$81.49	9.590%	$89.3049	$89.30	$89.30	$89.30
Purchase #7	$102.93	6.532%	$109.6534	$109.65	$109.65	$109.70
7 purchase totals =	$856.67		$935.8457	$935.83	$935.85	$935.90