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	$184.47	7.834%	$198.9214	$198.92	$198.90	$198.90
Purchase #2	$110.36	7.705%	$118.8632	$118.86	$118.85	$118.90
Purchase #3	$37.45	10.778%	$41.4864	$41.49	$41.50	$41.50
Purchase #4	$75.85	5.762%	$80.2205	$80.22	$80.20	$80.20
Purchase #5	$205.28	10.513%	$226.8611	$226.86	$226.85	$226.90
Purchase #6	$198.45	11.689%	$221.6468	$221.65	$221.65	$221.60
Purchase #7	$113.88	3.222%	$117.5492	$117.55	$117.55	$117.50
7 purchase totals =	$925.74		$1,005.5486	$1,005.55	$1,005.50	$1,005.50