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	$89.71	5.445%	$94.5947	$94.59	$94.60	$94.60
Purchase #2	$51.47	7.347%	$55.2515	$55.25	$55.25	$55.30
Purchase #3	$107.60	3.369%	$111.225	$111.23	$111.25	$111.20
Purchase #4	$215.87	9.338%	$236.0279	$236.03	$236.05	$236.00
Purchase #5	$5.59	7.738%	$6.0226	$6.02	$6.00	$6.00
Purchase #6	$196.99	9.399%	$215.5051	$215.51	$215.50	$215.50
Purchase #7	$36.83	4.230%	$38.3879	$38.39	$38.40	$38.40
7 purchase totals =	$704.06		$757.0147	$757.02	$757.05	$757.00