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	$67.89	5.173%	$71.4019	$71.40	$71.40	$71.40
Purchase #2	$56.74	4.207%	$59.1271	$59.13	$59.15	$59.10
Purchase #3	$55.83	12.836%	$62.9963	$63.00	$63.00	$63.00
Purchase #4	$101.86	3.851%	$105.7826	$105.78	$105.80	$105.80
Purchase #5	$222.62	5.752%	$235.4251	$235.43	$235.45	$235.40
Purchase #6	$246.39	3.654%	$255.3931	$255.39	$255.40	$255.40
Purchase #7	$6.36	13.249%	$7.2026	$7.20	$7.20	$7.20
7 purchase totals =	$757.69		$797.3287	$797.33	$797.40	$797.30