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	$111.86	3.313%	$115.5659	$115.57	$115.55	$115.60
Purchase #2	$15.91	13.624%	$18.0776	$18.08	$18.10	$18.10
Purchase #3	$175.94	7.365%	$188.898	$188.90	$188.90	$188.90
Purchase #4	$215.93	4.454%	$225.5475	$225.55	$225.55	$225.50
Purchase #5	$94.46	5.810%	$99.9481	$99.95	$99.95	$99.90
Purchase #6	$33.78	7.871%	$36.4388	$36.44	$36.45	$36.40
Purchase #7	$112.73	9.666%	$123.6265	$123.63	$123.65	$123.60
7 purchase totals =	$760.61		$808.1024	$808.12	$808.15	$808.00