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	$181.69	11.359%	$202.3282	$202.33	$202.35	$202.30
Purchase #2	$87.33	7.610%	$93.9758	$93.98	$94.00	$94.00
Purchase #3	$91.86	10.730%	$101.7166	$101.72	$101.70	$101.70
Purchase #4	$65.32	3.357%	$67.5128	$67.51	$67.50	$67.50
Purchase #5	$80.41	10.833%	$89.1208	$89.12	$89.10	$89.10
Purchase #6	$102.99	11.256%	$114.5826	$114.58	$114.60	$114.60
Purchase #7	$155.89	10.534%	$172.3115	$172.31	$172.30	$172.30
7 purchase totals =	$765.49		$841.5483	$841.55	$841.55	$841.50