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	$157.35	4.667%	$164.6935	$164.69	$164.70	$164.70
Purchase #2	$31.71	4.261%	$33.0612	$33.06	$33.05	$33.10
Purchase #3	$14.96	12.497%	$16.8296	$16.83	$16.85	$16.80
Purchase #4	$37.42	9.410%	$40.9412	$40.94	$40.95	$40.90
Purchase #5	$236.91	12.769%	$267.161	$267.16	$267.15	$267.20
Purchase #6	$173.48	6.813%	$185.2992	$185.30	$185.30	$185.30
Purchase #7	$102.50	11.752%	$114.5458	$114.55	$114.55	$114.50
7 purchase totals =	$754.33		$822.5315	$822.53	$822.55	$822.50