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	$177.57	11.259%	$197.5626	$197.56	$197.55	$197.60
Purchase #2	$141.51	7.420%	$152.01	$152.01	$152.00	$152.00
Purchase #3	$99.89	9.106%	$108.986	$108.99	$109.00	$109.00
Purchase #4	$204.45	4.811%	$214.2861	$214.29	$214.30	$214.30
Purchase #5	$110.35	3.596%	$114.3182	$114.32	$114.30	$114.30
Purchase #6	$112.57	9.523%	$123.29	$123.29	$123.30	$123.30
Purchase #7	$242.94	10.748%	$269.0512	$269.05	$269.05	$269.10
7 purchase totals =	$1,089.28		$1,179.5041	$1,179.51	$1,179.50	$1,179.60