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	$140.72	6.857%	$150.3692	$150.37	$150.35	$150.40
Purchase #2	$240.30	12.529%	$270.4072	$270.41	$270.40	$270.40
Purchase #3	$233.74	8.626%	$253.9024	$253.90	$253.90	$253.90
Purchase #4	$125.88	3.711%	$130.5514	$130.55	$130.55	$130.60
Purchase #5	$248.70	7.199%	$266.6039	$266.60	$266.60	$266.60
Purchase #6	$237.30	10.167%	$261.4263	$261.43	$261.45	$261.40
Purchase #7	$97.95	13.602%	$111.2732	$111.27	$111.25	$111.30
7 purchase totals =	$1,324.59		$1,444.5336	$1,444.53	$1,444.50	$1,444.60