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	$144.40	4.371%	$150.7117	$150.71	$150.70	$150.70
Purchase #2	$38.50	3.161%	$39.717	$39.72	$39.70	$39.70
Purchase #3	$129.49	6.392%	$137.767	$137.77	$137.75	$137.80
Purchase #4	$96.36	4.259%	$100.464	$100.46	$100.45	$100.50
Purchase #5	$19.73	4.375%	$20.5932	$20.59	$20.60	$20.60
Purchase #6	$111.47	4.724%	$116.7358	$116.74	$116.75	$116.70
Purchase #7	$27.76	4.187%	$28.9223	$28.92	$28.90	$28.90
7 purchase totals =	$567.71		$594.9110	$594.91	$594.85	$594.90