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	$92.34	4.691%	$96.6717	$96.67	$96.65	$96.70
Purchase #2	$191.62	12.488%	$215.5495	$215.55	$215.55	$215.50
Purchase #3	$61.78	6.253%	$65.6431	$65.64	$65.65	$65.60
Purchase #4	$166.78	4.265%	$173.8932	$173.89	$173.90	$173.90
Purchase #5	$247.63	3.291%	$255.7795	$255.78	$255.80	$255.80
Purchase #6	$10.52	9.548%	$11.5244	$11.52	$11.50	$11.50
Purchase #7	$67.31	7.408%	$72.2963	$72.30	$72.30	$72.30
7 purchase totals =	$837.98		$891.3577	$891.35	$891.35	$891.30