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	$93.35	3.111%	$96.2541	$96.25	$96.25	$96.30
Purchase #2	$148.61	12.290%	$166.8742	$166.87	$166.85	$166.90
Purchase #3	$98.78	10.758%	$109.4068	$109.41	$109.40	$109.40
Purchase #4	$246.26	6.381%	$261.9739	$261.97	$261.95	$262.00
Purchase #5	$63.51	4.134%	$66.1355	$66.14	$66.15	$66.10
Purchase #6	$241.46	12.616%	$271.9226	$271.92	$271.90	$271.90
Purchase #7	$42.55	9.637%	$46.6505	$46.65	$46.65	$46.70
7 purchase totals =	$934.52		$1,019.2176	$1,019.21	$1,019.15	$1,019.30