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	$215.89	11.841%	$241.4535	$241.45	$241.45	$241.50
Purchase #2	$187.93	12.687%	$211.7727	$211.77	$211.75	$211.80
Purchase #3	$88.51	12.704%	$99.7543	$99.75	$99.75	$99.80
Purchase #4	$210.51	6.288%	$223.7469	$223.75	$223.75	$223.70
Purchase #5	$215.71	3.238%	$222.6947	$222.69	$222.70	$222.70
Purchase #6	$174.77	13.239%	$197.9078	$197.91	$197.90	$197.90
Purchase #7	$63.55	3.641%	$65.8639	$65.86	$65.85	$65.90
7 purchase totals =	$1,156.87		$1,263.1938	$1,263.18	$1,263.15	$1,263.30