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	$202.32	6.245%	$214.9549	$214.95	$214.95	$215.00
Purchase #2	$82.45	5.439%	$86.9345	$86.93	$86.95	$86.90
Purchase #3	$223.89	9.578%	$245.3342	$245.33	$245.35	$245.30
Purchase #4	$117.54	10.630%	$130.0345	$130.03	$130.05	$130.00
Purchase #5	$40.84	3.519%	$42.2772	$42.28	$42.30	$42.30
Purchase #6	$201.32	4.102%	$209.5781	$209.58	$209.60	$209.60
Purchase #7	$172.63	13.763%	$196.3891	$196.39	$196.40	$196.40
7 purchase totals =	$1,040.99		$1,125.5025	$1,125.49	$1,125.60	$1,125.50