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	$101.83	4.103%	$106.0081	$106.01	$106.00	$106.00
Purchase #2	$95.99	9.402%	$105.015	$105.02	$105.00	$105.00
Purchase #3	$209.54	6.829%	$223.8495	$223.85	$223.85	$223.80
Purchase #4	$102.89	8.559%	$111.6964	$111.70	$111.70	$111.70
Purchase #5	$180.25	9.471%	$197.3215	$197.32	$197.30	$197.30
Purchase #6	$114.45	3.192%	$118.1032	$118.10	$118.10	$118.10
Purchase #7	$145.93	12.781%	$164.5813	$164.58	$164.60	$164.60
7 purchase totals =	$950.88		$1,026.5750	$1,026.58	$1,026.55	$1,026.50