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	$50.86	4.458%	$53.1273	$53.13	$53.15	$53.10
Purchase #2	$172.53	3.131%	$177.9319	$177.93	$177.95	$177.90
Purchase #3	$46.96	9.297%	$51.3259	$51.33	$51.35	$51.30
Purchase #4	$92.35	11.388%	$102.8668	$102.87	$102.85	$102.90
Purchase #5	$39.37	7.696%	$42.3999	$42.40	$42.40	$42.40
Purchase #6	$170.52	10.121%	$187.7783	$187.78	$187.80	$187.80
Purchase #7	$130.62	11.694%	$145.8947	$145.89	$145.90	$145.90
7 purchase totals =	$703.21		$761.3248	$761.33	$761.40	$761.30