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	$183.25	6.181%	$194.5767	$194.58	$194.60	$194.60
Purchase #2	$97.91	10.123%	$107.8214	$107.82	$107.80	$107.80
Purchase #3	$106.80	4.755%	$111.8783	$111.88	$111.90	$111.90
Purchase #4	$202.87	10.687%	$224.5507	$224.55	$224.55	$224.60
Purchase #5	$114.28	4.601%	$119.538	$119.54	$119.55	$119.50
Purchase #6	$96.40	10.547%	$106.5673	$106.57	$106.55	$106.60
Purchase #7	$75.58	3.513%	$78.2351	$78.24	$78.25	$78.20
7 purchase totals =	$877.09		$943.1675	$943.18	$943.20	$943.20