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	$68.69	4.654%	$71.8868	$71.89	$71.90	$71.90
Purchase #2	$50.29	9.367%	$55.0007	$55.00	$55.00	$55.00
Purchase #3	$238.51	13.367%	$270.3916	$270.39	$270.40	$270.40
Purchase #4	$81.96	6.555%	$87.3325	$87.33	$87.35	$87.30
Purchase #5	$166.51	3.385%	$172.1464	$172.15	$172.15	$172.10
Purchase #6	$10.92	13.430%	$12.3866	$12.39	$12.40	$12.40
Purchase #7	$43.53	3.278%	$44.9569	$44.96	$44.95	$45.00
7 purchase totals =	$660.41		$714.1015	$714.11	$714.15	$714.10