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	$207.36	10.406%	$228.9379	$228.94	$228.95	$228.90
Purchase #2	$143.45	6.581%	$152.8904	$152.89	$152.90	$152.90
Purchase #3	$232.89	13.621%	$264.6119	$264.61	$264.60	$264.60
Purchase #4	$72.55	13.258%	$82.1687	$82.17	$82.15	$82.20
Purchase #5	$199.37	10.621%	$220.5451	$220.55	$220.55	$220.50
Purchase #6	$88.88	5.767%	$94.0057	$94.01	$94.00	$94.00
Purchase #7	$105.98	11.699%	$118.3786	$118.38	$118.40	$118.40
7 purchase totals =	$1,050.48		$1,161.5383	$1,161.55	$1,161.55	$1,161.50