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	$29.35	12.458%	$33.0064	$33.01	$33.00	$33.00
Purchase #2	$51.25	10.459%	$56.6102	$56.61	$56.60	$56.60
Purchase #3	$44.56	4.700%	$46.6543	$46.65	$46.65	$46.70
Purchase #4	$36.90	10.220%	$40.6712	$40.67	$40.65	$40.70
Purchase #5	$21.70	13.288%	$24.5835	$24.58	$24.60	$24.60
Purchase #6	$127.76	13.250%	$144.6882	$144.69	$144.70	$144.70
Purchase #7	$21.96	11.223%	$24.4246	$24.42	$24.40	$24.40
7 purchase totals =	$333.48		$370.6384	$370.63	$370.60	$370.70