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	$72.26	13.262%	$81.8431	$81.84	$81.85	$81.80
Purchase #2	$101.40	9.571%	$111.105	$111.11	$111.10	$111.10
Purchase #3	$21.82	12.797%	$24.6123	$24.61	$24.60	$24.60
Purchase #4	$125.51	13.616%	$142.5994	$142.60	$142.60	$142.60
Purchase #5	$73.79	8.419%	$80.0024	$80.00	$80.00	$80.00
Purchase #6	$224.46	4.560%	$234.6954	$234.70	$234.70	$234.70
Purchase #7	$113.93	11.759%	$127.327	$127.33	$127.35	$127.30
7 purchase totals =	$733.17		$802.1846	$802.19	$802.20	$802.10