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	$236.73	3.177%	$244.2509	$244.25	$244.25	$244.30
Purchase #2	$89.67	3.596%	$92.8945	$92.89	$92.90	$92.90
Purchase #3	$178.45	5.315%	$187.9346	$187.93	$187.95	$187.90
Purchase #4	$220.31	7.465%	$236.7561	$236.76	$236.75	$236.80
Purchase #5	$174.83	12.244%	$196.2362	$196.24	$196.25	$196.20
Purchase #6	$138.47	10.390%	$152.857	$152.86	$152.85	$152.90
Purchase #7	$222.34	7.663%	$239.3779	$239.38	$239.40	$239.40
7 purchase totals =	$1,260.80		$1,350.3072	$1,350.31	$1,350.35	$1,350.40