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	$50.55	8.770%	$54.9832	$54.98	$55.00	$55.00
Purchase #2	$13.83	9.494%	$15.143	$15.14	$15.15	$15.10
Purchase #3	$207.86	12.156%	$233.1275	$233.13	$233.15	$233.10
Purchase #4	$141.66	12.200%	$158.9425	$158.94	$158.95	$158.90
Purchase #5	$84.70	5.859%	$89.6626	$89.66	$89.65	$89.70
Purchase #6	$99.25	7.770%	$106.9617	$106.96	$106.95	$107.00
Purchase #7	$102.52	6.632%	$109.3191	$109.32	$109.30	$109.30
7 purchase totals =	$700.37		$768.1396	$768.13	$768.15	$768.10