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	$132.33	9.490%	$144.8881	$144.89	$144.90	$144.90
Purchase #2	$104.57	9.344%	$114.341	$114.34	$114.35	$114.30
Purchase #3	$39.69	4.814%	$41.6007	$41.60	$41.60	$41.60
Purchase #4	$197.90	7.421%	$212.5862	$212.59	$212.60	$212.60
Purchase #5	$70.87	7.415%	$76.125	$76.13	$76.15	$76.10
Purchase #6	$229.46	9.214%	$250.6024	$250.60	$250.60	$250.60
Purchase #7	$164.58	8.481%	$178.538	$178.54	$178.55	$178.50
7 purchase totals =	$939.40		$1,018.6814	$1,018.69	$1,018.75	$1,018.60