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	$219.72	6.416%	$233.8172	$233.82	$233.80	$233.80
Purchase #2	$141.25	12.235%	$158.5319	$158.53	$158.55	$158.50
Purchase #3	$197.86	9.449%	$216.5558	$216.56	$216.55	$216.60
Purchase #4	$25.89	6.482%	$27.5682	$27.57	$27.55	$27.60
Purchase #5	$164.95	13.723%	$187.5861	$187.59	$187.60	$187.60
Purchase #6	$93.34	6.820%	$99.7058	$99.71	$99.70	$99.70
Purchase #7	$135.74	9.582%	$148.7466	$148.75	$148.75	$148.70
7 purchase totals =	$978.75		$1,072.5116	$1,072.53	$1,072.50	$1,072.50