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	$194.27	5.473%	$204.9024	$204.90	$204.90	$204.90
Purchase #2	$233.39	8.762%	$253.8396	$253.84	$253.85	$253.80
Purchase #3	$106.91	7.185%	$114.5915	$114.59	$114.60	$114.60
Purchase #4	$174.37	4.678%	$182.527	$182.53	$182.55	$182.50
Purchase #5	$75.58	10.442%	$83.4721	$83.47	$83.45	$83.50
Purchase #6	$35.98	8.168%	$38.9188	$38.92	$38.90	$38.90
Purchase #7	$210.31	3.807%	$218.3165	$218.32	$218.30	$218.30
7 purchase totals =	$1,030.81		$1,096.5679	$1,096.57	$1,096.55	$1,096.50