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	$74.85	9.526%	$81.9802	$81.98	$82.00	$82.00
Purchase #2	$181.90	12.637%	$204.8867	$204.89	$204.90	$204.90
Purchase #3	$140.34	7.620%	$151.0339	$151.03	$151.05	$151.00
Purchase #4	$197.84	12.504%	$222.5779	$222.58	$222.60	$222.60
Purchase #5	$130.29	9.203%	$142.2806	$142.28	$142.30	$142.30
Purchase #6	$118.89	6.215%	$126.279	$126.28	$126.30	$126.30
Purchase #7	$97.54	12.275%	$109.513	$109.51	$109.50	$109.50
7 purchase totals =	$941.65		$1,038.5513	$1,038.55	$1,038.65	$1,038.60