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	$98.29	5.125%	$103.3274	$103.33	$103.35	$103.30
Purchase #2	$20.31	9.558%	$22.2512	$22.25	$22.25	$22.30
Purchase #3	$22.90	10.818%	$25.3773	$25.38	$25.40	$25.40
Purchase #4	$158.62	9.300%	$173.3717	$173.37	$173.35	$173.40
Purchase #5	$134.28	5.384%	$141.5096	$141.51	$141.50	$141.50
Purchase #6	$53.31	3.565%	$55.2105	$55.21	$55.20	$55.20
Purchase #7	$17.44	10.382%	$19.2506	$19.25	$19.25	$19.30
7 purchase totals =	$505.15		$540.2983	$540.30	$540.30	$540.40