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	$245.88	3.762%	$255.13	$255.13	$255.15	$255.10
Purchase #2	$137.28	5.557%	$144.9086	$144.91	$144.90	$144.90
Purchase #3	$179.34	7.366%	$192.5502	$192.55	$192.55	$192.60
Purchase #4	$187.89	6.669%	$200.4204	$200.42	$200.40	$200.40
Purchase #5	$210.90	3.326%	$217.9145	$217.91	$217.90	$217.90
Purchase #6	$158.25	8.751%	$172.0985	$172.10	$172.10	$172.10
Purchase #7	$56.33	10.489%	$62.2385	$62.24	$62.25	$62.20
7 purchase totals =	$1,175.87		$1,245.2607	$1,245.26	$1,245.25	$1,245.20