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	$142.50	4.314%	$148.6475	$148.65	$148.65	$148.60
Purchase #2	$228.43	9.696%	$250.5786	$250.58	$250.60	$250.60
Purchase #3	$38.49	11.314%	$42.8448	$42.84	$42.85	$42.80
Purchase #4	$33.81	5.258%	$35.5877	$35.59	$35.60	$35.60
Purchase #5	$107.57	6.841%	$114.9289	$114.93	$114.95	$114.90
Purchase #6	$147.40	10.837%	$163.3737	$163.37	$163.35	$163.40
Purchase #7	$25.31	12.776%	$28.5436	$28.54	$28.55	$28.50
7 purchase totals =	$723.51		$784.5048	$784.50	$784.55	$784.40