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	$231.95	6.267%	$246.4863	$246.49	$246.50	$246.50
Purchase #2	$99.81	7.537%	$107.3327	$107.33	$107.35	$107.30
Purchase #3	$68.54	6.478%	$72.98	$72.98	$73.00	$73.00
Purchase #4	$169.70	5.744%	$179.4476	$179.45	$179.45	$179.40
Purchase #5	$119.94	6.481%	$127.7133	$127.71	$127.70	$127.70
Purchase #6	$224.89	11.538%	$250.8378	$250.84	$250.85	$250.80
Purchase #7	$85.91	7.269%	$92.1548	$92.15	$92.15	$92.20
7 purchase totals =	$1,000.74		$1,076.9525	$1,076.95	$1,077.00	$1,076.90