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	$178.46	12.284%	$200.382	$200.38	$200.40	$200.40
Purchase #2	$168.43	5.766%	$178.1417	$178.14	$178.15	$178.10
Purchase #3	$66.76	6.415%	$71.0427	$71.04	$71.05	$71.00
Purchase #4	$34.41	12.794%	$38.8124	$38.81	$38.80	$38.80
Purchase #5	$245.69	6.549%	$261.7802	$261.78	$261.80	$261.80
Purchase #6	$78.66	13.304%	$89.1249	$89.12	$89.10	$89.10
Purchase #7	$193.83	8.386%	$210.0846	$210.08	$210.10	$210.10
7 purchase totals =	$966.24		$1,049.3685	$1,049.35	$1,049.40	$1,049.30