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	$72.29	13.854%	$82.3051	$82.31	$82.30	$82.30
Purchase #2	$127.81	11.303%	$142.2564	$142.26	$142.25	$142.30
Purchase #3	$149.98	10.864%	$166.2738	$166.27	$166.25	$166.30
Purchase #4	$170.51	6.250%	$181.1669	$181.17	$181.15	$181.20
Purchase #5	$20.35	7.364%	$21.8486	$21.85	$21.85	$21.80
Purchase #6	$33.33	6.497%	$35.4955	$35.50	$35.50	$35.50
Purchase #7	$95.57	8.396%	$103.5941	$103.59	$103.60	$103.60
7 purchase totals =	$669.84		$732.9404	$732.95	$732.90	$733.00