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	$151.46	10.868%	$167.9207	$167.92	$167.90	$167.90
Purchase #2	$121.86	9.684%	$133.6609	$133.66	$133.65	$133.70
Purchase #3	$109.83	3.666%	$113.8564	$113.86	$113.85	$113.90
Purchase #4	$184.42	9.732%	$202.3678	$202.37	$202.35	$202.40
Purchase #5	$52.93	3.647%	$54.8604	$54.86	$54.85	$54.90
Purchase #6	$148.86	9.453%	$162.9317	$162.93	$162.95	$162.90
Purchase #7	$30.36	11.663%	$33.9009	$33.90	$33.90	$33.90
7 purchase totals =	$799.72		$869.4988	$869.50	$869.45	$869.60