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	$208.81	6.709%	$222.8191	$222.82	$222.80	$222.80
Purchase #2	$29.54	10.744%	$32.7138	$32.71	$32.70	$32.70
Purchase #3	$228.48	5.205%	$240.3724	$240.37	$240.35	$240.40
Purchase #4	$85.75	3.795%	$89.0042	$89.00	$89.00	$89.00
Purchase #5	$54.82	8.613%	$59.5416	$59.54	$59.55	$59.50
Purchase #6	$209.92	12.680%	$236.5379	$236.54	$236.55	$236.50
Purchase #7	$205.89	6.630%	$219.5405	$219.54	$219.55	$219.50
7 purchase totals =	$1,023.21		$1,100.5295	$1,100.52	$1,100.50	$1,100.40