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	$212.34	5.357%	$223.7151	$223.72	$223.70	$223.70
Purchase #2	$55.56	7.636%	$59.8026	$59.80	$59.80	$59.80
Purchase #3	$79.93	8.820%	$86.9798	$86.98	$87.00	$87.00
Purchase #4	$156.46	12.393%	$175.8501	$175.85	$175.85	$175.90
Purchase #5	$107.75	5.319%	$113.4812	$113.48	$113.50	$113.50
Purchase #6	$31.76	12.118%	$35.6087	$35.61	$35.60	$35.60
Purchase #7	$238.86	12.316%	$268.278	$268.28	$268.30	$268.30
7 purchase totals =	$882.66		$963.7155	$963.72	$963.75	$963.80