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	$137.49	3.582%	$142.4149	$142.41	$142.40	$142.40
Purchase #2	$142.31	7.270%	$152.6559	$152.66	$152.65	$152.70
Purchase #3	$222.59	8.838%	$242.2625	$242.26	$242.25	$242.30
Purchase #4	$224.83	6.789%	$240.0937	$240.09	$240.10	$240.10
Purchase #5	$140.38	5.563%	$148.1893	$148.19	$148.20	$148.20
Purchase #6	$161.72	4.187%	$168.4912	$168.49	$168.50	$168.50
Purchase #7	$155.27	4.865%	$162.8239	$162.82	$162.80	$162.80
7 purchase totals =	$1,184.59		$1,256.9314	$1,256.92	$1,256.90	$1,257.00