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	$57.98	7.575%	$62.372	$62.37	$62.35	$62.40
Purchase #2	$37.92	9.821%	$41.6441	$41.64	$41.65	$41.60
Purchase #3	$135.89	7.104%	$145.5436	$145.54	$145.55	$145.50
Purchase #4	$154.83	11.334%	$172.3784	$172.38	$172.40	$172.40
Purchase #5	$124.61	10.550%	$137.7564	$137.76	$137.75	$137.80
Purchase #6	$113.69	13.690%	$129.2542	$129.25	$129.25	$129.30
Purchase #7	$81.55	7.756%	$87.875	$87.88	$87.90	$87.90
7 purchase totals =	$706.47		$776.8237	$776.82	$776.85	$776.90