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	$144.93	7.514%	$155.82	$155.82	$155.80	$155.80
Purchase #2	$185.81	13.534%	$210.9575	$210.96	$210.95	$211.00
Purchase #3	$98.29	11.254%	$109.3516	$109.35	$109.35	$109.40
Purchase #4	$211.71	11.458%	$235.9677	$235.97	$235.95	$236.00
Purchase #5	$25.53	7.854%	$27.5351	$27.54	$27.55	$27.50
Purchase #6	$25.56	6.499%	$27.2211	$27.22	$27.20	$27.20
Purchase #7	$40.59	4.575%	$42.447	$42.45	$42.45	$42.40
7 purchase totals =	$732.42		$809.3000	$809.31	$809.25	$809.30