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	$84.63	6.460%	$90.0971	$90.10	$90.10	$90.10
Purchase #2	$163.42	6.787%	$174.5113	$174.51	$174.50	$174.50
Purchase #3	$200.40	9.626%	$219.6905	$219.69	$219.70	$219.70
Purchase #4	$35.29	8.178%	$38.176	$38.18	$38.20	$38.20
Purchase #5	$33.59	10.583%	$37.1448	$37.14	$37.15	$37.10
Purchase #6	$82.92	6.441%	$88.2609	$88.26	$88.25	$88.30
Purchase #7	$105.44	11.483%	$117.5477	$117.55	$117.55	$117.50
7 purchase totals =	$705.69		$765.4283	$765.43	$765.45	$765.40