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	$181.89	10.841%	$201.6087	$201.61	$201.60	$201.60
Purchase #2	$196.34	8.168%	$212.3771	$212.38	$212.40	$212.40
Purchase #3	$245.85	5.155%	$258.5236	$258.52	$258.50	$258.50
Purchase #4	$109.48	8.562%	$118.8537	$118.85	$118.85	$118.90
Purchase #5	$92.62	12.201%	$103.9206	$103.92	$103.90	$103.90
Purchase #6	$109.30	4.192%	$113.8819	$113.88	$113.90	$113.90
Purchase #7	$31.66	4.250%	$33.0056	$33.01	$33.00	$33.00
7 purchase totals =	$967.14		$1,042.1712	$1,042.17	$1,042.15	$1,042.20