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	$78.65	8.394%	$85.2519	$85.25	$85.25	$85.30
Purchase #2	$229.78	6.672%	$245.1109	$245.11	$245.10	$245.10
Purchase #3	$247.59	12.632%	$278.8656	$278.87	$278.85	$278.90
Purchase #4	$54.25	13.212%	$61.4175	$61.42	$61.40	$61.40
Purchase #5	$33.28	6.469%	$35.4329	$35.43	$35.45	$35.40
Purchase #6	$244.92	8.759%	$266.3725	$266.37	$266.35	$266.40
Purchase #7	$234.46	5.170%	$246.5816	$246.58	$246.60	$246.60
7 purchase totals =	$1,122.93		$1,219.0329	$1,219.03	$1,219.00	$1,219.10