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	$234.28	9.163%	$255.7471	$255.75	$255.75	$255.70
Purchase #2	$226.68	12.440%	$254.879	$254.88	$254.90	$254.90
Purchase #3	$170.98	6.870%	$182.7263	$182.73	$182.75	$182.70
Purchase #4	$71.35	10.581%	$78.8995	$78.90	$78.90	$78.90
Purchase #5	$203.78	10.356%	$224.8835	$224.88	$224.90	$224.90
Purchase #6	$35.76	11.125%	$39.7383	$39.74	$39.75	$39.70
Purchase #7	$141.88	5.846%	$150.1743	$150.17	$150.15	$150.20
7 purchase totals =	$1,084.71		$1,187.0480	$1,187.05	$1,187.10	$1,187.00