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	$97.83	6.727%	$104.411	$104.41	$104.40	$104.40
Purchase #2	$134.38	6.317%	$142.8688	$142.87	$142.85	$142.90
Purchase #3	$136.90	11.548%	$152.7092	$152.71	$152.70	$152.70
Purchase #4	$134.82	9.490%	$147.6144	$147.61	$147.60	$147.60
Purchase #5	$80.94	3.856%	$84.061	$84.06	$84.05	$84.10
Purchase #6	$72.32	12.219%	$81.1568	$81.16	$81.15	$81.20
Purchase #7	$75.44	13.335%	$85.4999	$85.50	$85.50	$85.50
7 purchase totals =	$732.63		$798.3211	$798.32	$798.25	$798.40