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	$214.94	8.734%	$233.7129	$233.71	$233.70	$233.70
Purchase #2	$226.47	3.145%	$233.5925	$233.59	$233.60	$233.60
Purchase #3	$124.44	4.714%	$130.3061	$130.31	$130.30	$130.30
Purchase #4	$86.30	6.833%	$92.1969	$92.20	$92.20	$92.20
Purchase #5	$119.81	3.434%	$123.9243	$123.92	$123.90	$123.90
Purchase #6	$139.95	5.316%	$147.3897	$147.39	$147.40	$147.40
Purchase #7	$54.90	6.698%	$58.5772	$58.58	$58.60	$58.60
7 purchase totals =	$966.81		$1,019.6996	$1,019.70	$1,019.70	$1,019.70