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	$243.73	4.276%	$254.1519	$254.15	$254.15	$254.20
Purchase #2	$232.31	7.718%	$250.2397	$250.24	$250.25	$250.20
Purchase #3	$17.95	10.756%	$19.8807	$19.88	$19.90	$19.90
Purchase #4	$69.35	13.158%	$78.4751	$78.48	$78.50	$78.50
Purchase #5	$94.78	10.721%	$104.9414	$104.94	$104.95	$104.90
Purchase #6	$162.64	6.824%	$173.7386	$173.74	$173.75	$173.70
Purchase #7	$134.58	7.688%	$144.9265	$144.93	$144.95	$144.90
7 purchase totals =	$955.34		$1,026.3539	$1,026.36	$1,026.45	$1,026.30