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	$55.26	6.465%	$58.8326	$58.83	$58.85	$58.80
Purchase #2	$86.83	4.489%	$90.7278	$90.73	$90.75	$90.70
Purchase #3	$58.54	5.465%	$61.7392	$61.74	$61.75	$61.70
Purchase #4	$100.73	11.322%	$112.1347	$112.13	$112.15	$112.10
Purchase #5	$242.46	10.337%	$267.5231	$267.52	$267.50	$267.50
Purchase #6	$58.71	10.640%	$64.9567	$64.96	$64.95	$65.00
Purchase #7	$174.82	7.484%	$187.9035	$187.90	$187.90	$187.90
7 purchase totals =	$777.35		$843.8176	$843.81	$843.85	$843.70