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	$173.81	3.320%	$179.5805	$179.58	$179.60	$179.60
Purchase #2	$201.69	6.367%	$214.5316	$214.53	$214.55	$214.50
Purchase #3	$156.53	7.337%	$168.0146	$168.01	$168.00	$168.00
Purchase #4	$169.48	8.758%	$184.3231	$184.32	$184.30	$184.30
Purchase #5	$92.89	8.473%	$100.7606	$100.76	$100.75	$100.80
Purchase #6	$162.34	7.298%	$174.1876	$174.19	$174.20	$174.20
Purchase #7	$226.72	10.503%	$250.5324	$250.53	$250.55	$250.50
7 purchase totals =	$1,183.46		$1,271.9304	$1,271.92	$1,271.95	$1,271.90