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	$80.82	7.287%	$86.7094	$86.71	$86.70	$86.70
Purchase #2	$83.65	7.355%	$89.8025	$89.80	$89.80	$89.80
Purchase #3	$147.84	5.625%	$156.156	$156.16	$156.15	$156.20
Purchase #4	$237.82	3.469%	$246.07	$246.07	$246.05	$246.10
Purchase #5	$227.74	12.642%	$256.5309	$256.53	$256.55	$256.50
Purchase #6	$216.27	3.866%	$224.631	$224.63	$224.65	$224.60
Purchase #7	$37.92	6.409%	$40.3503	$40.35	$40.35	$40.40
7 purchase totals =	$1,032.06		$1,100.2501	$1,100.25	$1,100.25	$1,100.30