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	$241.42	11.221%	$268.5097	$268.51	$268.50	$268.50
Purchase #2	$109.82	9.169%	$119.8894	$119.89	$119.90	$119.90
Purchase #3	$54.35	9.610%	$59.573	$59.57	$59.55	$59.60
Purchase #4	$144.85	12.231%	$162.5666	$162.57	$162.55	$162.60
Purchase #5	$134.36	4.708%	$140.6857	$140.69	$140.70	$140.70
Purchase #6	$211.96	6.743%	$226.2525	$226.25	$226.25	$226.30
Purchase #7	$185.58	7.453%	$199.4113	$199.41	$199.40	$199.40
7 purchase totals =	$1,082.34		$1,176.8882	$1,176.89	$1,176.85	$1,177.00