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	$151.40	12.171%	$169.8269	$169.83	$169.85	$169.80
Purchase #2	$143.48	4.550%	$150.0083	$150.01	$150.00	$150.00
Purchase #3	$82.86	3.667%	$85.8985	$85.90	$85.90	$85.90
Purchase #4	$195.25	3.650%	$202.3766	$202.38	$202.40	$202.40
Purchase #5	$219.59	6.267%	$233.3517	$233.35	$233.35	$233.40
Purchase #6	$104.30	12.337%	$117.1675	$117.17	$117.15	$117.20
Purchase #7	$228.69	11.684%	$255.4101	$255.41	$255.40	$255.40
7 purchase totals =	$1,125.57		$1,214.0396	$1,214.05	$1,214.05	$1,214.10