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	$32.73	3.518%	$33.8814	$33.88	$33.90	$33.90
Purchase #2	$211.35	9.643%	$231.7305	$231.73	$231.75	$231.70
Purchase #3	$86.51	13.742%	$98.3982	$98.40	$98.40	$98.40
Purchase #4	$144.32	12.281%	$162.0439	$162.04	$162.05	$162.00
Purchase #5	$153.43	10.638%	$169.7519	$169.75	$169.75	$169.80
Purchase #6	$69.63	3.760%	$72.2481	$72.25	$72.25	$72.20
Purchase #7	$203.76	7.237%	$218.5061	$218.51	$218.50	$218.50
7 purchase totals =	$901.73		$986.5601	$986.56	$986.60	$986.50